Well, my case is a little dfferent. I started taking Japan Society classes over zoom 3 years ago. As I am now 86 and use hearing aids, it wasn’t ideal; finally I switched to tutoring - just because I love learning Japanese. I follow the textbooks (Genji I, Genji II and now Quartet), where I learn the grammar - but wanikani has been enormously helpful in learning vocabulary as well as kanji. I find it a fun memory test; I do an hour or so, both morning and night, completing the reviews and always checking the ones that need more study as well. I wouldn’t have the discipline to do all that memory work without Wanikani’s helpful algorithm. It means that I am FINALLY beginning to recognize kanji in the texts I read (I’m on level 18, I think). I have not tried Duolingo. But I think Wanikani provides a great, rich exposure to the 3 entry points to a Japanese word or phrase - form/meaning/image, and they support one another. So maybe think some more before you give it up! -marilyn
Another senior on here!!! I’m 76 and studying hard. I am so glad to see you on here.
I find that combining WK with BunPro works really great. The latter can be used to both pick up grammar and to practice WK vocab in context (you can sync WK items to BunPro with an API key). And then, I feel like WK mnemonics are the most powerful way to memorize stuff, allowing me to recall items long after I encountered them last time.
Also, apologies for the shameless plug, but I made a lightweight web app to practice WK context sentences via listening to the TTS-generated audio: TTSensei web app: listening to randomized context sentences . Hopefully, you may find the app useful to add some context to WK items.
(Disclaimer: I’m learning Japanese for fun and with no particular purpose, so my way of learning is likely not the best)
This 56 year old Japanese learner is now feeling young. Thanks! 
Right now these 76 year old knees are not feeling too well.. There are days!!!