I disagree. Lots of books have quite a few "hapax legomenon", or... words that only appear once. If you're trying to build long-tail vocab, Anki will make sure you get repeated exposure to words that occur infrequently in a particular text. One might argue that these words don't matter as much since they're less common, but once you've mastered all the common vocab in a language, building a broader vocabulary becomes more important.
I don't disagree with you. Maybe I should have been more precise with the term 'language learning'. If you find yourself in the situation that you propose, I think you are already at native level in the target language. I'm mostly referring to those that try to go from zero to C1 or C2 with it.
My personal experience is that most people in the language learning community have trouble fitting SRS into their long term workflow because they don't stop to think much about the natural spacing of repetition they get in their other learning processes.
The people that popularize things like Anki the hardest are those that built and stuck with their own systems from the start. That's more of a referendum on their personality type than on the utility of their way of using Anki.
My hunch is that most people end up struggling because a lot of the most popular systems end up doing the exact opposite of spaced repetition once you consider the complete universe of foreign language input a learner is getting.
I've found that for me, Anki works really well for the first 1000 words, letting me jumpstart early vocab while most of my other time is spent on basic grammar.
For words 1000-5000 or 10000 in frequency, it's easy to get stuck in a trap I see a lot online: every time you encounter a new word, add it to Anki. This is a great way to burn out. You'll encounter most of these words with a natural spacing as you read native materials, if they're in the higher frequency bands. Doing reviews becomes excruciating, since you're losing the efficiency benefits of using the SRS unless you adjust review frequency based on the native input you consume (a good machine learning side project, perhaps?)
I've had a lot more success using Anki for words off in the long tail that I wouldn't otherwise have a chance to remember.
For Japanese I just downloaded a deck with 10 000 words, adapted the display a bit for myself (scraped pronunciations from the web, removed useless info to make them more minimalistic) and just started learning. When I read a book and found a word I wanted to learn it was almost always already in the list, and just needed to be moved to the front of new cards.
