Mei passes Ashe and echo in gm pickrate

This doesn’t really answer my question of how a hero can be good & bad at the same time

Also, doesn’t every hero require specific metas/balance states?

Brig & Sombra don’t require any kind of insane amount of coordination, as they can be pretty easily run on ladder as long as the player themselves is good enough. If I can play Brig & Sombra with success in Diamond and up (where coordination is better than Plat & below, but not insane like OWL) then I don’t think you can really say Brig & Sombra are bad. If you’re talking about lower ranks, the players just may not be good enough to get value as easily as they can on another hero