Part of the problem, sofaking, is that the matchmaking and ranked systems are very poorly designed in terms of their functionality for low level play and in general. The ranking system does not use any individual metrics to help in determining a players skill level, so things like kda, cs, objectives controled or secured, vision control and placement, etc have no impact on a players individual ranking in solo q. This is one of the inherent flaws of using the elo system as the solo q ranking system, it's a ranking system designed for chess. Individual on individual competition. As long as the system is ranking a single participant in relation to other single participants it works excellently, so it's fine for chess, or magic the gathering, or even if used for team ranked 5s in league.
The end result of this for solo q players is that the system is only particularly effective at the absolute highest levels of play (roughly the top 1% or so of the ranked player base) where team work, game knowledge, and mechanical ability of all players is at such a high level that it's a given every player involved in a match possesses those individual skill qualities and the games come down to a teams ability to execute a particular strategy. The unfortunate side effect of this is that players in lower level play, despite often having identical rankings and mmrs, can display a wide variance in terms of individual skill. This ultimately results in poor matchmaking since the matchmaking system uses the ranking systems data to pair players for matches and the ranking system itself is bad at identifying a player's skill level.
I feel your pain, and fully understand why it upsets you, it creates an unfair environment for about 95% of the competitive player base and invalidates the results of the vast majority of ranked games that are ever played. As a high level player myself I have ruined more than my fair share of games moving my many accounts up the ladder and early on this season I made a post in regards to exactly this, which I will attempt to find and post a link for you in a moment. I've been demanding that the metrics used to rank players be changed since about the end of season 2, and it's my hope we will, in time, see changes that will address this issue. Something as simple as using the champion mastery grade shown in the post game lobby (a good measure of individual performance in match) to manipulate or influence mmr gains to allow the system to more quickly and appropriately place players in the correct skill brackets could work wonders. This isn't the only thing that could be done, but it was a recommendation of mine back in season three when I also proposed something extremely similar (like almost identical) to the champion mastery system.
Let me see if I can find a link to my thread from several months back.
Found it!
http://boards.na.leagueoflegends.com/en/c/GD/aYt44eZZ-my-issue-with-the-ranked-and-matchmaking-systems-summed-up
