And I believe they already have systems in place that does that and are doing that.
There's still the problem that is inherit with games that are so team based though. If you have two or even ONE weak link on your team it can (not all the time) make it feel like the game is unbalanced, especially with how snowbally the game is.
Someone on your team may be a fine player but they get a bad game, a bad matchup, an enemy jungler that camps their lane. etc. So the real question is, is it really because of matchmaking or the state of the game?
A lot of the time the questions and solutions to them are not as simple as they appear and if Riot were to act rashly they could try and 'fix' something that's not broken because the problem actually was in another facet of the game.