I'll let you in on a secret.
You will probably have one toxic player in every game in the chat. They may be on the opposing team. If you just mute them, you will have no toxic players you can hear. At this point, all you have to do is not be the toxic player.
You will probably have one person who is under-performing or does not do exactly what you expect. Do not be an a** when calling them out. If they are under-performing either offer tips or keep quiet. If you are rude when calling them out, you will start a fight, and you will most likely lose the game as a result of the fighting that inevitably follows.
The trick, is to literally not use the chat unless you have to. There is honestly almost no reason to use it unless you need communicate a more complex strategy, or want to offer advice and to mute anyone who can even start a fight to prevent yourself being dragged in.
Source: I do this and have had almost no toxicity in my games since season three.