I don't see McCree as that big of a problem.
He is dominant, but there's characters who better control the pace of the game. He is "good" on every map, but he doesn't necessarily excel on any of them in particular.
Despite his pick percentages, honestly he is a strong pick who simply is "good enough" to function everywhere to some degree of success. That's about it.
In the way that if you had 5 characters who are the best at a map, then McCree is probably your best 6th pick over other sub-optimal characters.
If a map has narrow corridors and long sight-lines, you're going to pick Junkrat and Widowmaker over McCree.
If a map has lots of open air space and long travel times between points, then you're going to pick Pharah and Symmetra.
If the enemy team comp is very heavy on set-in defenses, then you'd pick Tracer or Genji to dislodge them.
Lots of corners? Pick Roadhog and Reaper.
There's not really any time where you'd say "The map has x and y, so McCree is the best option". However, he is a character that it never hurts to have.
He rounds out team comps decently well, has enough tools to get the job done, and works well with just about anyone against just about anyone...
In FGC terms, he is a character with plenty of 6-4's and some 4-6's in his belt, but not any 7-3 or 3-7s. That makes him a safe pick.
I've been playing since like early Alpha like a few years ago. Trust me, I've seen unbalanced characters. McCree isn't one of them. Bastion used to have a 1000 point shield in front of him and his bullets did more damage back then, and all you had to do was stance dance and you'd have a full shield back. Now THAT was a pain in the ass.
Reinheart and D.Va used to get meter for just taking damage, so you'd have an ultimate up every 30 seconds and they were game changers.
Bjorn's turret used to just be a monster. I think at one point you could just hammer it to level 3 and his ultimate made it a sort of "level 4" turret. Speaking of turrets, Symmetra's turrets used to do even more obscene damage and would go through shields and barriers.
So McCree being a little strong doesn't seem nerf-worthy to me. Hit him with a bomb and a satchel charge, he dies just like everyone else.
