Learning German and Spanish.
Same here. It started a few days before Christmas and it is still the same today. I expected they would solve the problem right after the new year, however, what I found was 1000+ words in the repeated stack after a short vacation.
I spent 5+ hours just to clear all 1000+ words and got to do 20 new words, and the other day 400+ more were back.
I still have a few days off for my vacation so I could just waste the whole day on Lingvist right now, but it would be difficult to keep up once I go back to work.
I do think the algorithm problem is more serious and more important than monetization at the moment. No one will pay for a broken product.
I voted En-to-Jp, but also think the 3000 - 5000 words cap will make it almost useless.
It's generally accepted that we need at least 10,000 words (N1 level) for basic reading in Japanese (unlike English, which 5000 will do), which is just equivalent to the Grade 3 level in K12! 5000 words for paid user is just at the level of 6-year-old of native speaker, far away from enough to do anything with it.
I hope that JP course can cap at N1 level (N2 for free user maybe?), while other languages will also get vocab size increase in the future (I am doing En-to-De, it would be nice to get to C1 level, ~10000 ).
Obviously, Lingvist counts the same words with different endings as different words. In this sense, it took me around 50 hours to 2000 words. and now I am at 2510 words and 75 hours, way slower than the post said.
BTW, I am learning German from English, and my mother tongue is Chinese.