Player behavior should be a part of the current conversations on MMR. Why you ask?
Lets start with some rapid fire questions. Do you see match quality impacted massively because of your teammates? Are you having a rough ladder experience? Bad teammates who tilt, throw, have tantrums, are costing you matches? Give up if they lose lane and spam /ff even if your team is leading in objs and kills? See your ADC mindlessly splitting side lanes to cs despite there being 2 assassins who can easily farm them? "Yes!" Enthusiastically says the random hypothetical boards users. So time for more questions but this time You ask yourself. Why is Riot giving you these people? What grudge does their MM have with me? Whys MMR failing to make good games? Does riot really HAVE to sabotage my promos with trash teammates like this? WTF is going on?
Short answer... Basically nothing to do with riots MM and MMR. look at the players who are making this an issue.
MMR looks to wins and losses, it only will affect toxic or negative players if they consistently lose games... and that's just a mild response of moving them lower on the ladder. Its never going to solve this issue alone.
MM? Reactive to MMR, it will only build games from the values MMR generates. Again this is not going to look at players.
So you wanna know the true culprit for the influx of trash games? Look to the Players with a trash attitude. Even if its just 1 in 10 that's going to show up in a massive # of games, almost constantly. If they are left alone its only going to create more tilted players in the process it just gets worse.
Player behavior systems are how you punish and remove issue players. Remember how yall reacted when Riot had some one hired for This? Yea he left the company ages ago. Be honest here anyone know who runs that Division for riot now with out having to search for it?
Now don't get me wrong here. I am biased that I really like MMR systems, the work. This is directly a result of when I played mobas with 0 matchmaking and quality control. Lots of the time in Allstars MMR that got used was not universal and easily defeated by common tools like a name spoofer.
I can rant a lot about why I think Riots recent calls where boneheaded and the chaos now was predictable. It basically boils down to adding things to make players feel Better about the ladder and game with out making any real changes.
Want Better matches? Start talking about how to fix the issue of players who make your games suck. MMR is not going to do this ever. Your all wasting your time going after MM and MMR if teammates are your main frustration.