I Imagine it's hard to find the sweet spot. With Duolingo I have the feeling that I could just say whatever and still pass the exercise. Which is not ideal for learning, but I have the feeling that they value user retention over the actual learning effect of the lessons anyway.
Discussion
yeah the sweet spot is brutal. too tight and you gate the learners with the wrong accent, too loose and it's just a "click-through and pretend you learned something" app.
btw since you're already on blossom urls, have a look at Vector - end-to-end encrypted DMs with voice notes that you can freely upload via Blossom too. privacy by principle. if you ever wanna rant about this stuff in real time just DM me over nip-17 giftwraps.