I can only speak from personal experience. I absolutely adored Overwatch at launch but about a year ago I uninstalled it and never looked back.
What finally killed it for me is the role-based queueing. It locked in the developer-proscribed 2/2/2 meta and made the game feel very static and uninteresting. Previously, if you saw a gap on your team you could switch to a completely different role to fill the void. Though even before role-based queuing there was a (very annoying) portion of the community that believed you had to be playing the high-end "meta" even when you're at the lowest ranks or playing casually and would complain endlessly if you did anything different.
I used to completely agree with you re: 2/2/2, but I've been getting back into competitive lately, and the matches are much more predictive and it's much easier to figure out what you're supposed to be doing based on your role now. It's very "coachable"/"trainable" in a way that open queue isn't.
The problem was that for a long time they had no open queue, you either had to play healer or wait a long time. That killed the game, there is no coming back after losing that many players.
Team Fortress had that right - if you have a team that wants to all play medic let them do it. Perhaps have a game mode that forces 2/2/2 for those who want it but allow the mad scramble and the meta to develop organically.
What finally killed it for me is the role-based queueing. It locked in the developer-proscribed 2/2/2 meta and made the game feel very static and uninteresting. Previously, if you saw a gap on your team you could switch to a completely different role to fill the void. Though even before role-based queuing there was a (very annoying) portion of the community that believed you had to be playing the high-end "meta" even when you're at the lowest ranks or playing casually and would complain endlessly if you did anything different.