Matchmaking in League of Legends

Look, I know I'm not the best player in the world. I get salty over small things and I'm not the best player, but the thing that infuriates me the most is the matchmaking in League of Legends. I usually get placed with one or two (bot lane duo) players that are either really really bad, or trolling. Like my last game I got a 0/14 Renekton on my team, while I was 14/6 Warwick IN RANKED. He didn't type in chat at all to respond and he just ran in without poking or anything, dying over and over again. We lost that game due to him, most of my games are like this, or we steamroll the enemy team. I don't understand Rito's matchmaking system at ALL! Why don't they place players who go 0/14 at Renekton with other people who do just as bad? Why do I sometimes get placed with people who can't get a single kill. I know Renekton is a pretty solid Bruser/Tank. I've played him before and have done well! I wonder sometimes, why even have Matchmaking, which is supposed to match you to players equal to your skill, if you are just gonna match me with a terrible player or two most of the times?