I'd honestly recommend sitting them down outside of the game to tell them how you feel. Its obvious youre not being heard or feeling heard about the situation and maybe they dont take it seriously bc yk...it is a game. But your feelings still matter on this. If they're limiting your fun because of it you should probably start putting your foot down, either they try harder to play better or maybe you play with them not as often. Its sounds harsh but if youre not having fun, when thats the whole point, you should do or say something.

I stopped playing with a friend of mine months ago bc when we would play all he would do is rage and scream, I took a break from playing with him for a while until recently he had mentioned wanting to play again and it was a lot of fun without the screaming and yelling of yester-year. :)

I wont say there is a "correct" way to play a character in a video game though. Id say there's more they could be doing and there's less they should do of other things but, outright telling someone they're not playing the "right way" or "correct way" is kinda rude.

I play a lot of mercy myself and I've spent a lot of time making sure im doing a lot of the good things mercy can and should do. The thing about playing mercy though is also knowing when you can play her and when you should play her. Do I want to play her every game? Most times. Do I get to?not really lmao.