Since season 4 when i started with league. Honestly it's pretty easy to not get punished even when you're toxic. Just don't chat? I mean in the end it doesn't matter if u tell them they are bad at the game, because they would never say "yes you are right" because in all honestly, if they are in my elo, your elo or somebodys elses elo, we can assume that over a long number of games those players around our Elo are equal to us. Sometimes we do good, sometimes we do great, sometimes we do bad. We feed and we carry, we tilt hard and sometimes we tilt never. It happens to all of us.
If the average league player does bad in 1out of 10games which i would say is a fair number right? then in every single game on "average" we will meet a player who just has that 1game out of his "10" where he will do bad, because there are 10Players playing right now one of them will have the bad game, assuming we as individuals are doing 1bad game in 10games.
And no matter how many times someone flames him or how bad people trashtalk him, it won't make him play any better. therefore flaming is a waste of time.
If your reasoning for flaming is for example "he just needs to stop dying and i can maybe still carry" well then don't flame him but rather say, "try to play save i can carry this". It's up to your teammates if they are able to do it or not. But i hella know trashtalking will things make only worse, because when i do bad, and players trashtalk me, holy cow did i got tilted in the past from it. until i learned the great option of using /mute all at every single game right from the start :>