League is a toxic game, everyone knows this. The second something goes wrong the typers come out in chat to bring everyone down. The amount of positive interactions in chat pales in comparison to the negative ones.
You can turn off all chat by default but not your own team chat. Mute All exists but it is something you need to do every game. There should be a permanent tick box, like with turn off all chat, that we can have in the settings. Giving players more options is a good thing.