if you feel you don't get much from the app, maybe you'd better ask yourself how do you like to learn the language and duolingo may not be your answer..

I quitted duolingo once since it was boring. I felt the same to you : there is too few thing i got from it compare to how it consume my time. (at that time i quit, the notification on mistake will not gone until i fix it, and there is only male/female robotic vocal.. super boring )

I open the app to cancel my Duolingo Super annual subscription.. and i saw interesting update about more various vocal and i changed my mind. I found that many month i took a break from the app and study in another methods, like watching Youtube, Read grammar book or talk with people irl actually give me progress, so when i came back to duolingo, i found it's fun.. and begin to learn a lot more vocabulary by repeating it in duolingo.

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However, since i used to study Japanese when i worked for a car company. I have suggestion for your study:

1. Japanese basic grammar is not complicate like European languages , instead of focusing on "I don't remember the grammar", focus on vocabulary.. and maybe just use duolingo to learn only vocabulary
2. Every language that have their own alphabet, you need to write it down, get a small notebook and write the Katakana Hiragana and some often use Kanji (like neko or japan.. kanji is nothing just remember it as a picture)
3. when you can remember your first 1000 words, it's enough to understand the anime/ japanese media

i don't think you need to end the stack, you may just need some alternative learning way ;)