I'm likely to be matched with players of lesser skill and so it balances out.

That's only true if you consider "skill" as a purely mechanical concept. Plenty of people are good shotcallers or might excel at synergizing with teammates but lack a certain mechanical skill.

If you want to ignore team interplay and say "We're in the same SR so what I'm doing must be fine" then team sports might not be for you. The real world equivalent would be "We're both on the B-grade cricket team so it doesn't matter if I make shit calls and get my partner run out because even doing that I'm on the B-grade team. If I didn't make shit calls I'd be on the A-grade team so what are you complaining about?"

Overwatch is an e-sports game. It's about teamwork. Saying "I got here on my mechanical skill, fuck the teamwork aspect and everyone else should be fine with that because I'm more mechanically skilled to make up for being a useless teammate" ignores the fact that you're depriving everyone of the opportunity to improve through teamwork. There are plenty of video games out there, if you don't want to play in a team, why pick a team-oriented game?