I'm no expert, but I've been thinking about whether there is such a thing as too much gamification. As I'm sure everyone knows my now, I've been learning Japanese for a few years and one of the tools I use (I use quite a few, including in-person evening classes) is Duolingo.
On one hand the gamification aspect of Duolingo definitely helps to make you come back and do daily lessons (I'm on a 1211 day streak, and you'd have to pry my phone from my cold dead hands before I'll lose that).
But I increasingly feel that some of the other aspects of gamification in Duolingo, like leagues and leaderboards, make me go for easy points, rather than doing what is best for my language learning. In an ideal world, gamification would support your learning and prompt you to do what is best for you, but I just don't think that's entirely possible. And while overall they're probably vaguely aligned, there must be some discrepancy between what's good for Duolingo (engagement numbers) and what is good for me learning a language.
These are just some idle thoughts.... but it's been nagging at me, because I do feel like the amount of gamification on Duolingo may actually be bad for learning. But, I'm not sure.