Generally, when people want to tell everyone else what to do, while they seem utterly clueless and/ or just do what they want in the first place.

Had that 2 times yesterday (in 2 games I managed to play before being fed up again).

First game:

Widow main telling me to go healer (what's my main), but we had no tank and just squishies, so no point in playing healer in the first place, also, after around 95% on healers/ tanks for the vast majority of my games played, I want to play DPS every now and then too.

I logged in S76 (one of the 3 DPS I can play rather decently).

We lose, Widow main pms me after the game telling me "tks for the loss" for "not playing healer".

Second game:

I log in Rein, other guy picks Orisa, the only healer on our team is Zen. So I switch to S76 again. Then Zen proceeds to tell me to switch back to Rein. I tell him that one Orb won't be enough to keep alive 2 tanks and 3 squishies. He's telling me he would be an awesome Zen and he will do fine.

I constantly was having the gold medal for heals throughout the enitre game. As S76.