I disagree with this in principle. Gamification is something we should be very wary of because it is inherently bad. It reduces what you care about in an activity to points and a progress bar.
Instead of sticking with language learning because you have some intrinsic reason to want to learn it (or even a external one such as wanting a new job) you're substituting that with whatever Duolingo puts for their gamification. To the degree you engage with and are motivated by the gamification you are substituting your own metrics of success and progress for points and streaks.
And soon enough we end up here, where Duolingo has gamified their internal numbers and in doing so gamified your "learning".
Instead of sticking with language learning because you have some intrinsic reason to want to learn it (or even a external one such as wanting a new job) you're substituting that with whatever Duolingo puts for their gamification. To the degree you engage with and are motivated by the gamification you are substituting your own metrics of success and progress for points and streaks.
And soon enough we end up here, where Duolingo has gamified their internal numbers and in doing so gamified your "learning".