Compare it to things like Diablo 2, where there was no in-game chat moderation whatsoever beyond your ability to mute people. I don't remember any problem with 'toxic' chat behaviour on that game, or on many other online games like it. If anyone started spamming or similar, people just muted them and got on with their lives.
... we must have had very different experiences with D2. Every time I tried to get into the multiplayer (several times, over many years) the other people involved basically ran me out of the game. Was
incredibly miserable, even worse than the hack-ridden mess that was D1. And it got
worse as time progressed, even as blizzard fixed up some holes in the program that made griefing easier. My experience with LoL, things have actually improved in terms of general atmosphere since they started in with the heavier reporting and whatnot. Not
much, because this is still competitive online multiplayer we're talking about, here, but some. Which is significantly more than I can say about the MP games I've touched that were effectively hands off.
Being fair, I don't exactly play LoL very often or particularly consistently, so it's entirely possible I've just lucked out playing on better days or some crap. Still, the concept that just relying on the mute feature alone actually does absolutely
anything is vaguely farcical to me. People that can't shit talk you will just jump up and down in your face, or whatever the equivalent action is for that game.