It's not really how we learn new things. We see, hear, experience them in context many times, not force ourselves to recall them. Forced repetition is one of the worst most inefficient approaches to language learning.

I've found spaced repetition a great way to increase the size of my vocabulary whilst learning a language. You're right that it's unnatural, but a large unnaturally-learned vocabulary can then be polished by practice in more natural contents, and I feel like the net result is more efficient than using the natural contexts alone. This is especially true since I do not have easy access to native speakers for half an hour every day, but I can practice with the Anki app whilst on public transport during that time.

Last time I learned a language (German), a small vocabulary was my perpetual weakness. Now I'm learning a different language (Spanish) with a different approach that makes heavy use of spaced repetition, and vocabulary is no longer my weakest point. Instead, listening comprehension is now my weakness. But with a decent vocabulary, I am now working on improving the listening comprehension using podcasts. If my vocabulary were weaker, this would be much more difficult as I would need access to a native speaker who would considerately restrict themselves to mostly use vocabulary I know.

One thing that’s helped a lot with my listening comprehension is following along in a printed book with an audiobook reader. Especially when it’s a translation of a story I already know, I can usually more or less follow the plot and let the language information seep into my unconscious.

Thanks for the tip! That's one thing that hadn't occurred to me to try. I've tried the same thing with TV/movies, but the subtitles are usually not identical to the spoken dialog - they tend to be simplified and paraphrased to be shorter - but eBooks should be very faithful to their written counterparts.

From my experience, spaced repetition is only really useful as a trigger to recall prior meaningful experiences. The really tricky part of using spaced repetition well is writing the cards: you need to work with new material until it feels obvious, and only then make cards that will recall that experience of it being obvious.

For language learning, there’s one other wrinkle: you need to be working with material written in the target language, rather than written about the target language. Most of my language cards are Cloze deletions from novels I’ve read or museum captions, for instance.

The idea that scheduling recall repeatedly is a poor and inefficient approach to learning is directly contradicted by all available research on learning and memory.

See [0] for a review of the research on spaced repetition.

[0] https://www.gwern.net/Spaced-repetition