When are you most frustrated playing League? Probably when you do really great in your lane position, but two or three of the other positions feed like they trying to put a stop to world hunger. Or maybe when your team is ahead, but then one of your team members makes a questionable choice, gets caught out, and you lose important objectives as a result. We've all been 'that guy'. And we've all had to suffer through having 'that guy' on our team. League is a team game, of course, but a team game where poor play on the part of even one player can quickly lead to disaster. The snowbally nature of League doesn't help all that much, either.
This is frustrating, of course, because you're going to feel like you had a lack of agency in deciding the course of the game.
I strongly suspect this is where the generally toxic attitude in League arises from. People get mad, not just because they're losing, but because they're losing and they feel hopeless. It becomes easy to scapegoat the player who did something stupid and cost you the game. It becomes VERY easy to overlook your own contributions to that loss when someone else keeps getting caught in the enemy Jungle with no vision coverage. One lane feeds and tempers flare because after all, that's all on them. It's out of your control how shitty they're doing in lane. It's also out of your control to prevent them from getting caught out, barring getting killed yourself trying to rescue them.
Here's a bit of insight from Dominionland.
Ragers, flamers, and the like were nearly non-existent in Dominion. Partly due to the pacing of the game, I suspect. No one had time to rage in allchat since there were always objectives to take. But more importantly, that lack of agency never really reared its head there. Bottom lane had constant interaction. There was always something you could do top. Snowballing was all but nonexistent, so the game was never over until you were staring at the defeat screen. One bad play rarely decided victory or defeat. If you wanted to win, you had to *consistently* out-play the enemy team. With more hopeful matches you got more hopeful players. In my years of playing Dominion, I can count the number of times I saw a team surrender on one hand because there was nearly *always* a chance to turn things around.
But Rift isn't like that.
The team that knocks down the first tower wins the majority of games. Teams that get first blood AND first tower are all but fated to win. There's no hope there. It feels out of your control. And when people feel hopeless, they lash out.
I don't know how to fix this. I don't have any suggestions to make it better. But if ever Riot feels like lowering the venom level of League a bit, the place to begin is to find a way to make Summoner's Rift a *team game* right from the start rather than a game where you happen to be on a team.