I use Anki to study all kinds of subjects, and more than half of the value is processing what I learned (usually with pencil and paper) into good anki cards ("atomic", as per Michael Nielsen's definition), including the insights that I had when studying the subject (like "what's the comparison with X that I used to understand Y?")
I'm not sure if it is efficient, mind you, but I suppose it's effective because I can recall information later when relevant, and I believe that like exercising just being able to stick to a study routine ends up being more important than picking the best routine
I had the exact same experience. The more work I did up front on a card, the better I was able to remember. When I was learning the kanji cards, I would take the time to draw them out in a special notebook while thinking carefully about the different components, and it really helped with retention.
I did not do this with many cards though, hoping that they would eventually stick.
I think in general the more you engage with the thing you are doing, the better you remember. Even when reading or listening to a lecture or whatever. Maybe what I'm proposing here is that by making it dynamic you create a system where deeper engagement is necessary.
I'm not sure if it is efficient, mind you, but I suppose it's effective because I can recall information later when relevant, and I believe that like exercising just being able to stick to a study routine ends up being more important than picking the best routine