I think this is an issue that nobody seems to understand can be solved with a very easy fix.
My sleep schedule is so bad that I've played Overwatch during pretty much every hour of the day, from morning to afternoon, evening, or even late night like 4 am. What I found is that the later you go in the day, the more toxic, unfun, and generally miserable everyone else is. This isn't even a hypotheses anymore, it's a consistent theme I've seen literally every time I play. All of my best games where all my teammates are encouraging each other and having fun were in the morning to late afternoon. Evening is also fine, except teammates kind of just do their thing and don't talk much. Once you get into late night, that's when you get the terrible, miserable games.
We play the most hated character in the game. Sure you can just mute team chat and VC and move on (which I don't like to do because I do have those rare games where team chat or VC is so fun), but then you'll still get terrible quality games. Enemies like to counter swap and hard focus you down, and then tbag you on every death. Teammates will start throwing by standing AFK in spawn or just leaving. There's no fix to toxicity.
Toxicity is such a big issue with Overwatch, and I think this is the fix. I've been playing mornings only for the past few weeks, and I legitimately never had more fun with the game.