Riot matches you not according to elo, but according to team total mmr.
If you are high elo/mmr, you will be matched with pure idiots so that the team total mmr averages vs the other team.
This system makes people with high elo to have to carry every single game they play if they want to win, while at the same time teaching idiots and help them to win.
THEREFOR, if my team doesnt play as much as me, I make them lose on purpose, FOREVER.
I will never teach anyone that is clearly lower skilled than me.
Enjoy riot matchmaking.
PS: Riot thinks its better to have some of us like me to do what we do then to have a balanced matchmaking, what they forget is the accountability of how many people we make to uninstall this game and stop playing because we give them the worse game experience ever.