Literally every guide on spaced memory tells users to avoid making the mistakes he made. Nobody argues that you can learn big concepts through spaced repetition.

Personally, I used Anki to learn the Amino Acid structures and abbreviations, for which it was invaluable. Basically, Anki is gold for things you must learn by rote or for things that you already learned but have trouble remembering.

Anki isn't, and was never meant to be, for learning. It's for turning things you've learned but have trouble remembering into long term memory.

Feels like this mostly has to do with the flat nature of flashcards, not so much about spaced repetition. Spaced repetition could be applied to playing the piano or whatever.