Learning resources when hitting a plateau?

I’ve been learning Japanese for about 4 years. I learned how to read kana and a few hundred kanji in the first year, and due to overwork from my career I took about two years off and have been going strong for the last year, however I’m beginning to hit a plateau where I’m having difficulty retaining my knowledge of kanji and vocabulary.

I primarily study using Wanikani, and I’m a little over 50% of that, so I can accurately read around 1000 kanji.

The issue is that I have very little knowledge of grammar, sentence structure, how different particles modify and connect words, etc. Basically, I can’t read a damn thing and so I’m hitting an issue now where I can see, recognize, and read plenty of different words but can’t read the majority of full sentences.

What would be the best way to address this? Just pick up a copy of Genki I and go at it? Read through Tae Kim’s? Or does someone here have a better recommendation for textbook or resource?