“Is WaniKani SRS adequate?”
I agree with you and say that the answer to this question is definitely “no.” I use Wanikani strictly for the memorization of kanji meanings, readings and some miscellaneous vocabulary…
… and that’s it. Nothing more.
The emphasis of mnemonics is great, however I always make my own. Also, to read faster, I separately train my ability to recall meaning and on’yomi reading as fast as I can. If you do this, you won’t be applying the mnemonics at all, but if you have to slow down, then I’d put at least an 80% chance that the mnemonic will help you remember the kanji again.
I’d go almost say that Wanikani’s only purpose is for reading and literally nothing else.
This all being said, I still completely recommend Wanikani. You have an organized set of over 2000 kanji laid out for you to minimally insert into your Japanese learning schedule and if you stick to what the average Wanikani user does, then you’ll be far higher than average in your speed of learning compared to other Japanese learners.
My main motivation for using Wanikani is because I know for a fact that wouldn’t be doing a single thing else to actually learn kanji. Wanikani is just a plant that you have to water everyday. (Which also has arms and will punch you in the gut if you stop for any more than a day.) Hope these cluttered opinions and info helps.