Hmm. I find learning fun, no matter what the scope is - even Greek, which remains obscure to me. (Quick, ask me something about Greek! I'll nod wisely and stroke my chin in deep thought and then get distracted and wander elsewhere.) But you're not wrong: there's a fun discovery phase, then a "hey, does this actually work" phase, and then a "crap, I need to figure out how to MAKE it work" phase, all of which are decision points where one might choose to not bother.

It totally depends whether you're still experimenting and learning or not, which is totally circumstantial. Sometimes I slog through things at the start, on the promise that they will start to be fun once I see the point.

Easiness is fun because it enables more messing around and learning. Not having to solve a problem is not fun, because problems are learning opportunities and are fun, unless they're just trivial obstructions in the way of the real problems of interest.