No, I CAN'T just mute anybody I don't like
I can't just mute the people who are arguing about something pointless. I need to read it all, so I know what to say to get them to stop and start playing the game.
I can't just mute the person who rages at a mistake that me or one of my teammates made. I need to read what the guy says, so I can prevent him from going afk or playing worse.
I can't just mute the enemy team when they start trash-talking. I need to be able to reassure my teammates that what they say shouldn't matter to us.
In half my games, I feel like I'm fighting two battles at once. One is the given objective: Take down the opponent's nexus. The other may not be as obvious, but it is just as important: Keeping the team together.
Muting people doesn't help me win games, so that's why I've never muted anyone. But with the kind of things I come across, it doesn't help me feel like I've won, either.