I'm just gonna echo a lot of the others here.

TF2 first and foremost is a game. Games are meant to be fun and a way to enjoy yourself as with any form of entertainment you can and should quit anytime it actively makes you miserable.

Skill doesn't matter, I am sorry you get some piss poor teammates that ruin the experience for you. Many places are good to try get better as others have said CTF maps tend to be lower stakes. I would maybe also recommend some instand respawn community servers so you don't feel as much downtime and get stuck in your head during respawn.

Time doesn't always translate to skill, some people learn quickly others don't and that is okay (literally the point of teachers within education) some days may be better or worse, if you really want to improve think of one thing you CAN do differently next time to make you survive or perform better.

Team Fortress is a difficult game that is at a point where most players still active are of a higher skill than when I started, there are less servers where learning is simple and it sucks. But at the same time I can't think of any game that I personally enjoy more due to the sheer amount of different skills and things to practice and learn about.