The snowballing effect makes games seem like this, even though it's not really true.
Right, MOBAs and RTS games tend to have an inherent 'snowball' factor. This is the main reason you are seeing lopsided games--it was not necessarily because of the matchmaker. We've had discussions in the past about how 'snowball' League is and whether we need to adjust it, but that's a discussion for another day.
If Team A and Team B play 10 games, every game might be lopsided; however, if Team A wins 5 games and Team B wins 5 games, technically it's a fair match-up.
If there is a matching system, why is a win or loss always a landslide?
If Team A and Team B play 10 games, every game might be lopsided; however, if Team A wins 5 games and Team B wins 5 games, technically it's a fair match-up.