First, a bit of context:

So at the time of writing this, I already know this will probably take a looot of time to write, and I don't even know if I'm gonna finish it. So, if I do finish it, please take the time to read all of it before discussing it 🙂

THIS IS NOT A RANT !!! I am not trying to tell people who successfully learned through RTK to forget what they know, or to tell them they are bad at Japanese. Heisig did a lot for Japanese learning at a time where there were very few ressources for it, and I also used it.
This is just to explain why I believe his method is now outdated, and why I believe younger learners would be better off not choosing RTK or its children (Wanikani, or any method teaching radicals, kanji and words as separate entities) over other methods

PS: I will explain what RTK is later in more details if you don't know, don't worry

Who the fuck am I:

For those who are curious about my own experience before deciding if this is worth reading:

I'm a french dude who has been learning japanese for a bit more than 5 years, with a very inequal dedication to it.
As for my current level, I auto tested myself with both a N3 and a N2 JLPT exam without prepping (didn't know what kind of questions they'd ask, or worked toward them specifically before the test), so I can tell that I could pass N3 tomorrow if need be, N2 with less certainty depending on luck since my rating was passing but not by much, and would need to work quite a lot for N1 (didn't pass full test but skimmed it) though I know some N1 content (I feel like it's pretty hard to get a good grade in N1 without actively working for it, as most of the content isn't really useful).

I am mostly an immersion learner, since that's how I learned English too (hence why my JLPT knowledge is spread across all levels) but I personnally used WaniKani (level 60 reached, but didn't continue using it so forgot some things, and last levels really didn't do it for me so I forgot a lot), RTK + Kanji Koohii and JPDB (and Anki, obvs) to try and learn Kanji in addition to immersion, or to help remember what I learned through immersion.
I also did all the "try to binge through core 10k and get burnt out" shit you could think of

Now to get into the nitty gritty…

Context and Learning:

I wanted to have at least a small part dedicated to this, since it's very important, though probably obvious to most of you.

Context is very linked to how the human brain works: the more you give it context, the more it can create connections, the more it will remember a piece of information.

That's true for any kind of information.
Explain to a kid not to touch a snake, he'll probably get it. Throw that same kid in a swarm of venomous snakes, he won't ever touch one again (because he'll be dead).

As a kid, you ran around and fell countless times, ultimately teaching yourself when to run around, when not to, and what you need to pay attention to in order not to fall if you decide to do it.

The more complex an information, the more it needs context, and the more this context needs to be accurate (though unaccurate context can be beneficial to an intermediate learner, since he'll realize why it's unaccurate).

This is also why to learn something, getting as close to the context you'll be doing it in is the best.
Learning the moves on the ground before swimming might work, learning them while being in the water (with a rubber ring) will work better
Playing guitar in your room is not useless, but you'd better try and train in front of some people if you want to be able to correctly play live. Both are closely related, but you'll need to do the second one at one point if that's your objective.

Technically, wouldn't always being be the best way to learn guitar ? Well you might lose focus if you do this, but it's true that it would work wonders for your ability to play live, if it was doable.

Anyway, the closer your learning conditions are from your end goal, the faster you will progress toward that goal, as long as you can continue.

This last part is actually the most important, better to learn through to the end with a subpar method than to learn really fast then stop in the middle of the road

Language learning, how to "cut down" context into parts and make them repeatable:

As mentionned in the part before, the more complex an information, the more context it needs to be learnt, and god knows languages are complex, since they're everywhere.

Technically hand signs and mimics are part of languages, but here we'll stay in the realm of writing, speaking, words …

Out of my head, here are the main language application contexts I can think of:

• Listening to the language

• Speaking the language

• Reading the language (with or without narrative context, complete sentences or isolated words but in a specific context)

• Writing the language (usually complete sentences, but sometimes could be notes of few or even one word)

Technically, there is a better order to it (inputting before outputting, the second leading more easily to bad habits than the first) but doing any of those things while being focused on it would contribute a lot to that activity, and would passively contribute to the others, ultimately helping to learn the language.

We could obviously cut those contexts into more contexts, and that's actually what we're doing when using Anki to mine sentences for example.
You don't read the subs, listen to the audio and watch the images from the whole show the sentence came from, you only read, listen and watch the parts with which you struggled with the most. And as they become easier, you do it less and less, ultimately leading to only doing it every few months to jolt your memory. That's SRS in a nutshell.

What to remember from this part is: to use SRS efficiently is to use it in a way that imitates the most the actual context that led to the creation of that card, in a really short time.

You didn't read an isolate word, you read a sentence comprising that word, with corresponding video and audio that pertained to a narrative you knew about beforehand.

So you need to try, within your flashcard, to keep as much of this context as possible while losing as little time as possible.
Here we kept the text you read, the audio, we turned the video from the scene into a still image (not a lot of movements during dialogues anyway, usually), but we had to pass on the narrative (hopefully, the rest is enough for you to remember what the narrative context was without directly being told)

Assuming this was the only part of the episode you didn't get, within one flashcard, you almost fit the whole learning appeal of that episode ! (the things missing being the immersing and fun part of it, making it feel more like studying which some people might hate)

Where RTK fails (in my opinion):

This might come a bit late, but for those who don't know, RTK stands for Remembering The Kanji, and is a well known method to learn kanji, based on mnemonics and cutting the kanji into different parts, ultimately binding them in your brain to a keyword.
Those kanji parts will also be given keywords, sometimes with some ethymology behind it and sometimes not at all (the creator actually encourages creating your own keywords)

There are 3 books, 1 for the most used kanji, 1 for the readings of those kanji (only onyomi, and not in words) and a 3rd one who basically goes further into less used kanji

Most of you probably got it with all the yada yada about context, but RTK has NOTHING to do with actually practicing japanese, and that is its biggest flaw.

It is the Japanese equivalent of learning Latin to learn Spanish more easily…. ultimately taking more time than it would have taken to just learn Spanish directly.

I'm gonna give examples to make my point clearer, some for which the RTK method works pretty well, and others where you end up learning something wrong

Here is a kanji most of you guys probably know already:

日

This is a pictogram, meant to be representing the sun. In RTK, the keyword used here is Day. Not perfect in my opinion, but if I show this on its own to a native japanese, he'll probably read it as ひ or ニチ, which can both mean Day depending on context, so it's not all bad. What pops into your mind is the same as what would pop into a native japanese's mind

But in this case, what point is there to learn it as shown in RTK ? Like, wouldn't it be strange to learn "patate" as meaning potato in french, but without learning how it is actually read until who knows how much time later ?
Learning this kanji immediately as a word (which it is) is normal, because it is a word before being a radical, before being a piece of mnemonic

Another example:

休

This one is more problematic, but not the worst kind of kanji you can find in RTK.

It represents the idea of rest (a man 亻resting on a tree 木). And yes, I insist on it representing the idea of it, because it doesn't mean anything alone. This is not a word (or at best a very rarely used one).

This is more similar to learning "sub" in english. Except here in the book, you are told "sub" means "sublime", when it doesn't. It is a part of it, sure, but alone it doesn't mean anything

Japanese people don't differentiate kanji words and kanji, they are all just kanji:

Now some of you might wonder "Sure, it doesn't mean rest per se, but knowing it is linked to that meaning is useful".
And that's true, it is useful to know, and the little story about the man and the tree is great to remember it.
However, seeing that kanji again and again on a flashcard by itself to learn that idea isn't. You would have been way better off being shown the kanji with the little story once, learning 休む immediately after, repeatedly seeing it inside of sentences you put in flashcards, or even by itself since it does have a meaning.
If you were to add that little mnemonic at the back of the card, you'd fulfill the exact same objective except you also learnt how to actually use the word

When you learn to drive, you're first taught everything piece by piece. However, you don't spend hours just braking, or just turning right.
Immediately after vaguely being taught how to do everything in, you put them into practice all at the same time, in a simplified context (parking lot) then in a real-life context.
If you fail at one of those things, then you take a new quick look at thing again, but you try again, you try it all at the same time.
After a while, those vaguely known things become automatic, you won't be braking then turning the wheel. To you, the timing at which to brake (or knowing if you even need to do it) becomes a part of "turning". It becomes a whole

Reading Japanese is the same. You first brush upon the basic characters (hiragana and katakana), then you start learning a few words. At each words, you eventually decompose them to see what they're made of, but once that's done, the reviewing part of it needs to be done all at the same time.
If it's a word with 2 kanji, then you decompose the action by checking what those kanji mean, then put them back together and when you review them, you keep them together as a word (or even better, as a sentence).

If you fail to remember the word, or one of the reading for the kanji, you brush that part again then go back at it .

While doing that, you'll continue seeing new words with those kanji, helping you better grasp what context they're used in.

Instead of reviewing one kanji at a time, in one card each, you will review multiple kanji at a time, or one kanji and some hiragana, in multiple cards at the same time

The difference between 格 and 酪 ? Why should I care ?!:

Funnily, after a while the okurigana for the verb, or the other kanji will themselves become mnemonic for the reading of the remaining part of the word.
One will start to feel unnatural without the other, or even have no meaning !
I know what 石鹸 means, but 鹸 ? I'd probably think it's a new kanji !

Remember when I explained that an information is always best learned with more context ? Having more kanji on your card or in your word IS more context

If a kanji appears alone, then of course you need to be able to recognize it alone, but if it doesn't ? Then who cares ! I never tried to know what nment means, there is always enlighte or something else before anyway !
However I do know what light means, because it does appear "alone" (in a sentence, so relatively alone)

羅 ? Don't know that. 森羅万象 ? Hell yeah !

This word is something i added to my list a month ago. Never failed it once. Never bothered to check that 羅 actually seems to be used to represent rome and the latin language either. Why would I need to make something that looks like this -> 森羅万象 stand out more ? It already looks plenty different enough to me.

You'll start seeing the word as one big kanji, just like you see "sublime" as one word and not as "sub"+"lime" (anyone who learned that with "There ain't anything more sublime than a lime" as a mnemonic has my utmost respect for life though). This is how japanese people see it too.

Writing:

Yes guys, you've read the title of that part correctly. All of you who were screaming "WHAT ABOUT WRITIIIIING" at the top of their lungs will have an answer. Ready ?

Do the same as in reading. Goodbye.

Ok jk, I am gonna detail this a bit more, I am already a few hours in this anyway might as well go through to the end.

Everything I said above, with the added context helping memory and all of that, well that works the same for writing

Let me give you 2 examples, one old (a kanji I feel like I've always known) and one new: 曜 and 機.
I think we can all agree that, while far from being the worst, those kanji are the kind we all go "oh fuck me" when they appear to our eyes for the first time, especially at the beginning.

So, why did I show you those two kanji might you ask ? Because I know how to write them, and yet I don't have any mnemonics for them

They all have a clear place in my mind, and I know when I need to write them. They were stuck to my brain by context (and SRS for the second one)

Recently I decided, once again, to try and learn to write kanji. Before, this was actually why I had tackled RTK, because I logically thought that to learn to write the words, I'd need to know how to write the kanji that composed these words, even though I never needed this to learn how to read them.

This seemed logical, but it never worked for me, and I doubt I am the only one in that case. I kept failing kanji after kanji, even simple ones. Some of them worked, didn't know why, but most didn't.

Forward to not that long ago, I showed a friend at a party how to write 曜, and he asked me if I had some king of mnemonic for it. The answer was no.
After going home, and sat there and wondered like an idiot WHY I knew how to write this one specifically. And the answer was … context. I knew in what words I saw it. It was the kanji from 曜日. This is how it was stuck in my brain.

Stupid, right ? But that's what led me to how I learn to write kanji now (and to this post too probably): I learn to write them in words. Just like I learnt to read them

It's just more efficient for the brain to do it that way. Just like if I write "I walk a lonely r" you probably have the rest flowing into your mind, if you write 飛行 then your muscular memory will write 機 all alone.

Learning to write this word by learning its 3 pieces, and then remembering the mnemonic for each one is slower and harder. Not only that, all of those steps will end up being ditched over time for the more efficient "just write the whole word" by your brain anyway.

飛行機 is more unique, is more specific than 機, so it's easier for my brain to access it. I gave it more context, just like with reading

Dealing with exceptions:

Some people might ask, "but what about kanji that both look similar and are used in similar context ?"

You'll deal with them when you find them. An example I like is 治癒 and 治療.

These two words look awfully similar, to the point where the first one could be an older, more difficult version of the second one, but they are two different words (albeit with very similar meanings) with their own readings. This is probably the only example that comes to my mind of a pair of two-kanji words that I really mixed up during immersion for something other than me reading too fast or a brain fart.

You'll just have to find those exceptions by yourself. Funnily, when writing the title "The difference between 格 and 酪 ? Why should I care ?!", I actually discovered that the second kanji is a word in its own right. So there might be a use to learn it, and if one day I come across it during immersion and confuse it with the first one, then I'll do it

池 他 and 地 are also good examples. They look alike, and these ones could even appear in similar contexts. I learned to actually differentiate them when I failed one of them for the first time in wanikani by confusing it with one of the others

Conclusion:

For those of you who read all of this, here is a cookie !

Again, this not a diss to people who actually taught themselves with RTK, it being imperfect doesn't mean it won't work, obviously some people managed to make it through.

My only objective here was to help new learners (or even intermediate like me) to not lose as much time as I did, even though there is an easier/better method (especially for the writing part, I guess you guys could see it)

The only case where I would recommend to continue RTK is if you really find the puzzle approach fun. But anyhow, knowing about its shortcomings is always a good thing, just keep in mind those keywords are sometimes a bit wobbly on their foundations

PS: This is my first posting such a huge thing on Reddit, so if you guys have advice to make it more readable don't hesitate !