But what I don't like is the implication that learning isn't already fun. Learning is inherently fun!
It's not gamification that make learning fun. What makes learning fun the satisfaction that comes from completing tasks successfully and the sense of focus that comes from a course that has a well-organized roadmap.
Rewarding any activity diminishes intrinsic motivation. Focus shifts on the reward, our brains deem the activity as worth-less in the absence of a reward. The activity is now a chore.
See the work of Alfie Kohn and Stanford’s online course on gamification.
For me, what makes learning fun is the retroactive satisfaction I get from solving a future unrelated problem that incorporates the knowledge/skills I acquired at an earlier point.