So I was casually reading viktor kysly's pattent, and that's what I found:
Basically, if player "Sucks" He will get better MM, if player plays well, he gets worse MM.
Really Vitya? You call this Fair game?
Src:
Edit: Some good people answered read if you want to get educated too.
tl;dr
Guys its safe to play the game :D.
They Complained that there would NEVER be Skilled based Matchmaker in WOT..
Apparently according to Vasily there is.
Part of the reason they brought in Ranked Battles was as a skilled based matchmaker, then they allowed everyone to play their FV Chieftains and the completely balance Obj 279(e) in Ranked and ruined it.