Hardest part for me is de-conjugation and decoding sentences (i.e. Grammar). Grammar didn’t seep into me enough, maybe because I didn’t actively use it. WaniKani and Anki is more about vocab.
Katakana is hard to learn by just learning sentences and grammar. I really recommend drilling Katakana vocab separately, e.g. on Memrise, and your Katakana recognizing skills will improve dramatically. Similar to how WaniKani teaches you Kanji, I think.
I think learning a language is about
- Memorizing
- Decoding the real thing
- A similar thing, but looking from an opposite side, is adapting your memory to the real thing
BTW, have you seen: ?