Maybe I'm different, but my first tracks were posted to TMX, not because they were good, but because I made them. I had no idea if they were good or not. I just posted anything I finished. I'm not just saying this in retrospect. I truly didn't give any thought to the quality of the track. It's horrifying to think back on actually.
Most of those old tracks have since been deleted off TMX.
I had no idea there were things you could do to make your track fun or huntable, or that there were specific styles of tracks. I just built all kinds of stuff, regardless of smoothness, track length, or even any regard to how many cuts there were.
So I don't think you can say that
everyone uploads tracks because they think they're good. Some people just build some random stuff and post it because it seems to be the thing to do (like I did).
I think the average track we see uploaded these days has got better and better though, mostly because the TM building community has matured a lot over the last 5 years. Also, it's very easy to make a good track in Canyon. Even tracks with flaws can be a lot of fun to drive, because of how the physics are designed.
But I think the majority of tracks are built by authors who know at least some of the basic concepts of good track design. Probably most authors do try to make sure their track is good in their eyes before they release it.
Others may still be like I was all those years ago, not sure what is good and what is not. I guess that's what this topic is all about, to give some insights by those who
have built tracks for many years and have gained some insight into what makes a track good/fun to drive.