Ask HN: Is building a calm, non-gamified learning app a mistake?

Not doing subscriptions for an app that has ongoing server costs is going to bite you, you may want to reconsider that.

Your biggest issue is going to be that language learning for adults is largely an unsolved problem. I know people with 1000+ day streaks on Duolingo who are nonetheless not fluent, and from everything I’ve read, it seems clear that spaced-repetition techniques are not sufficient (and possibly not necessary) to achieve fluency. Most people say you need immersion, which is difficult for an app to provide (research other people who have tried, you probably wouldn’t be the first and can save a lot of time, effort and heartbreak by learning from other people’s failures).

It's solved, look up comprehensible input: https://www.dreaming.com/blog-posts/what-is-comprehensible-i...

The problem is duolingo is particularly horrible and is intended to get people addicted, not educate.

I'm always a bit weary of theoretical stuff like this. The best way to learn a new language is to move there (preferably somewhere where people don't speak or don't want to speak your native language). I know people that didn't speak a lick of Spanish, moved to Spain, and in a year they're basically fluent. Of course, still struggling with stuff they might not be used to: gendered language, conjugations, and so on. But overall, able to be fully understood by native speakers.

Theoretical educational frameworks don't replace the day-to-day struggle of trying to get shit done. (Doing this is, of course, extremely uncomfortable, and people will avoid it at all costs.)