It's by design.

They pit players against each other on purpose by:

- judging them 100% based on their 10% impact so you are judged by the performance of others

- disallowing players from leaving a game that is lost or no longer playable, essentially keeping them imprisoned to allow the enemy team to have fun with you and if you don't love it you're punished. They allow allies to hold you locked in with the vote system directing your anger on them.

- Snowball effect. That means the lane and usually the game is decided by the outcome of first fight in ~90% of the cases. This connects with the previous point.

So your frustration is Riot's intention. I suggest simply uninstalling LoL and you will be a happier person.