I fucking hate this line of reasoning because it strawman's the hell out of everything. I want more players to not quit. But if you don't have the mechanics/priorities to win, then it's not worth playing. Period.
If the enemy Jungler has a 4 to 1 gank rate on a lane, then the game is probably over. If no one calls MIAs, wards, or someone keeps split pushing and getting killed, then it's not worth it. I don't mind if you screw up, but if people are telling you what you're doing wrong, and you continue to do it, then you're not worth playing with.
Sucking isn't a reason to quit. People who refuse to educate themselves due to sheer laziness aren't worth playing with. People who never quit - never - are trolls.