Sadly it's kind of a thing that happens with MOBAs- people don't really learn sportsmanship.
LoL is a little better these days because if you are level 30 you do find some games where everyone is chill or the game is really hilarious and friendly or most people are just quiet and ping. If you just started it's even worse because a lot of people are immature and migrating from other MOBAs where they don't get punished for being awful and start to salt and rage on their teammates, and they haven't gotten banned and punished in LoL for being toxic yet. (There is punishment for toxicity going up. I started a smurf to play with my friend who just started together, went one game in it and was shocked at how awful people were behaving comparatively to my usual account). I would suggest as the others said, muting all and enjoying the game. So it does get better when you've leveled up till there is ranked and most of them have started to be punished for toxicity and learned to not rage and so on. It's a little easier in the ARAM and featured game modes, where everyone is playing casually, so there is less of the toxicity, and normal games when there is ranked for people playing seriously. You can communicate objectives even if you mute all and also use pings for objectives- most games use pings for objectives anywho.
From what I recall (though it was a long time ago) of my experience smurfing (versus my experience now, where I usually don't mute all unless i need to coz people are quiet and amiable in norms but you can get a jerk 1/5 games or 1/2 games or something), I would recommend muting all and enjoying the game. or muting your teammates :3.