I am ballmain in masters and only swap very rarely, even if I have a lot of counters. Many teammates always tell me to swap. Personally, I want to learn to play with ball, no matter what the enemies counterpick, because I think individual skill is more important than always being flexible and counterpicking.
This just isn’t true though. Example: everyone counter picks against D.Va with Zarya. This is great, except when I play D.Va I’m not going head to head with Zarya. I have mobility to get away from Zarya - and start harassing her supports, forcing her to blow bubbles on them (no pun intended but funny to imagine) so we can then burst her down as a team and get a pick or two on supports in the meantime. Or she’s not using bubble for that, but spinning around panicking using them on herself while no one is even hitting her because I’m DMing her dps’s shots while mine get picks.
Counter picks are no match for strategy, game sense, and exploiting enemy mistakes.