I think the problem is new players are put on teams with good players. The good players carry, and the losing team complains.
Matchmaking is 100% ****ed.
Say you have a team of 4 lvl 30s and a lvl 5.
Against a team of 5 lvl 20s. Because of the lvl 5, the first team very well may lose. Even if the other 4 are professionals.
In my opinion lvl 10 and below should never be in a match with anyone over level 10 (unless pre-made)
Nobody in 11-20 should be in a match with anyone outside of that.
And nobody 21-30 should be in a match with anyone below 21 unless pre-made of course.
At least the worst level 21-30 would know how to play well enough, so that they aren't completely horrible.
I'm not exactly sure how matchmaking is done, but in my last game there were 2 lvl 11s and I'm a lvl 30, it just didn't seem fair that I was against them, they did very blaitant rooky mistakes.