The MMR "adjustment" for other killers based on your main(s) is far too punishing.
Long story short, I main Hag and Demo, and as anyone who plays at the high end will tell you, they don't do so great at the top unless you are playing anything but the sweatiest build and playstyle. It's reached a point where I can't have fun as these killers any more. I can 4K and it bores me, because it's the same survivors with the same builds spewing the same nonsense post-game (and often outside the game), and I can't mess around with fun builds because my MMR is too high and it's not worth the sheer time investment it would take to lower it to a point where I can do this.
So I go to play someone I have significantly less experience with to try and have fun and maybe learn a new killer. But the MMR adjustment based on my mains puts me against high MMR survivors, on every single killer. I get stomped on because I don't already know everything about new killers, and it's boring. Please explain to me how Hag and Nurse play exactly the same. Or Huntress, or Twins, or literally any killer in the game. I'm facing 6000+ hour survivors on Pig, for crying out loud.
It is genuinely more efficient (and more fun) to make a new account and learn a new killer that way. Except for it to actually work, I'd have to make a new account for every single killer in the game. Then maybe after a hundred or so matches I can swap back to my main account and give them a go with everything I've already unlocked from this massive grind of a game.
Do you not see how messed up that is? That I'm being punished for being good at one or two killers so I can't even play anyone else without it being a horrible experience? Why should I even bother playing killer at all? The fun has been sacrificed for accurate matchmaking but the matchmaking isn't even accurate!
I'm honestly starting to question if this adjustment actually exists, or if it's just one rating across all killers. Wouldn't surprise me if that was the case.
TL;DR - Make fairer adjustments to MMR for playing other killers. I don't want babies, but I also don't want to be stomped on every game by survivors way more experienced than me because I want to learn a new killer. I have almost no idea what I'm doing as a Nurse, but the game seems to think I'm already good as her somehow. That doesn't make sense, Behaviour!