match making system is fucked up beyond repair

You have a piece of shit on your team. He assists the enemy team winning in every way he can. He draws you into a verbal confrontation so he can get you mad and then report you for standing up for yourself. At the end of the game, you report him, you block him, you mute him, you did all that. You then join a new game, and there is that exact same player again in your next game. It happens all the time. BUT WHY???? Why would the match making system put you in another game with a person that you clearly indicated you did not want to play with the game before? Why would the match making system make you play two ruined games in a row with the same bag of shit person on your team? How is this allowed? Fuck you Riot.