Because they took OW1, changed very little, made it a lot more microtransactiony, didn't release a promised co-op mode that basically was the reasoning to release OW2. I'm sure there's more but that's about it.
I don't like some of the micro transaction changes they've made, but as a competitive-focused OW player, 5v5 was for sure a great move when it comes to game balance and the overall feel/pace of competitive matches.
Wish they wouldn't put heroes in the battle pass though. That is stupid as fuck.
Yeah, I've said before that as much as people liked to hate on Chris Metzen, it seems that when he left it was a massive migration of optimistic talents out of the company. Now, that's not to say that he caused people to leave, as opposed to him leaving for the same reason that everyone else did, but I've looked at it as a big turning point in blizzard's history of being generally good-natured.