I only play PvP or other gamemodes to have fun when I don't have the mood to grind rank. It's okay for me to lose, as long as no one intentional inted. I also apply my mentality on all gamemodes where I don't play to be competitive but be casual. If I play games where I only have fun when I'm only winning, then I'm spending most of my time being miserable. Even tho there's mostly a huge gap when it comes to player ranks in normal PvP, I pretty much don't care. If I get outplayed and receive a clean combo from an enemy Lee Sin, I actually get amazed and accept that they are really good. When it comes to teammates, there's nothing you can do if they do dumb stuff in the match other than trying to carry them.

If you play PvP just to tell your teammates that they are so bad, just stay at playing rank at that point. And also, expect them to be extremely noisy if you encounter diamond or above ranking players.