How to raise division/MMR without playing better

1. Allow your teammates to carry you. You are playing to win, not to be a big shot who carries every game. In fact, you probably cannot carry every game unless you are smurfing. If you are 1-9 but your teammates are all 9-1, don't bitch about your score - just stay safe, relax, listen to calls, and let your teammates win the game for you. 
2. When your teammates are throwing, remember your opponents can be just as likely to counterthrow. The matchmaking algorithm dictates that your teammates and your opponents have similar skill level. If your teammate is throwing, your opponents can throw too. Until the nexus falls you can always seize the opportunity to win.
3. Don't question bad plays. Remember your teammates also want to win - they are not intentionally feeding your opponents as an attempt to make your life harder. When they make bad plays, they already feel bad themselves, so there is no need for you to spray salt onto their wounds. I recommend you say absolutely nothing about it and keep your mouth shut. You are here to win the game, not to belittle some random person on the internet who made an honest mistake.