I played (not well) and refereed (even less well), but I'm not sure this is the right question, frankly. I've never been president of the United States, but I certainly have my (impeccable) opinions about how the country ought to be run. And opinions on pretty much everything else. And I recognize that others have the right to their own (mostly wrong compared to mine of course) opinions on just about every subject.
I agree that as a sports fan some sort of expertise can be important. And that is usually the result of personal experience more than of study. But I think there are two sensibilities at play here that produce our different outlooks, regardless of our differing experiences.
1. a fundamental sense of humility about just how hard it is to play basketball consistently well. Of course, that humility is easiest gain through personal experience. But you don't need to be a violinist to appreciate how hard it is to play a violin at master level. Frankly, you just need imagination.
2. different temperaments. some folks see the glass half empty, others half full. No bridging that divide: it's just the way the world turns.
There's no answer, I don't think, for the broadly-sketched differences between those posters who are more critical or pessimistic, and those who are just less so. I don't think that expertise necessarily makes you one or the other. Temperament does.