I learned Hungarian (one of the more difficult languages to learn) by loading up a database of ~10k cards. While it worked great in the beginning, within a year, I was just constantly telling the algorithm that I didn't need to review cards for 3-5 years. But the thing is, with a language, I'm not going to forget all those words in 5 years. There will be no point in reviewing them. So I just started deleting cards if I knew them already. And eventually I was spending so much time deleting cards that I just gave up on SRS altogether.
It could be that I have some latent savant-like language learning abilities, though I doubt that. I think my experience is likely related to language learning itself. With a language, if you are immersed, you have constant daily repetition with or without the cards.
All that to say, I think SRS algorithms should have a language learning mode that automatically archives vocabulary cards once you've mastered them to a certain degree. I'm not sure what would work best. Maybe once you've crossed the 6 month threshold, it could just automatically archive the card.