@kendrictonn Sort of. I think Duolingo is optimized to be a sort of game, and that people who are serious about learning a language self-select into other apps.
The most important thing is missing.
Copying is trying to solve the same problem in a same way. Spending 20-40h a month is definitely not enough to make the better app. If your app is not better, people will quit. So the high numbers will be temporary