As far as whether there are good guys, it's kind of a tough question. Compare to US intervention in Latin America, which was a horrible disaster (and still is) where anyone we could have backed was some psychotic murderous group of thugs. In the middle east, it's like that plus they're all religious maniacs on top of that. If we choose "stability" we have to choose authoritarian monsters. The Kurds only look good by comparison - they're fucking nutjobs too. But like you say it's actually a regional conflict (and the wildcard of the global jihadist forces were beaten).
Anyway the state of play is still the same as it was after we crippled Iraq- a multilevel proxy war. It's a war between Iran/Syria and SA/Israel. And Russia backs Iran/Syria while we back SA/Israel. If we completely leave the conflict, Russia/Syria/Iran have an advantage, Iran possibly develops nukes and shifts control of the middle east. It's hard to sell us just "leaving" when you take a wider view of what's happening, especially with Turkey going fundamentalist batshit crazy and Russia seizing extremely important territory outside its borders. I'm sure things will work out fucking great if we "just go home" right? LOL.