How to fix ranked matchmaking:
There are 3 problems that plague ranked matchmaking.
Season Reset At the beginning of each season, players from all skill levels have to compete against each other in placement matches to determine their initial division. From there, they will rise or fall to their appropriate division facing more/less skilled opponents along the way. Chaos ensues. But why reset everybody? What's the point? Why make everybody start over again creating unfair matches? Riot, if you really feel the need to reset the top of the ladder, then reset the top of the ladder (masters). There is absolutely no reason to reset everybody.
Smurfs I don't know how to get rid of them but something needs to be done because high elo players creating smurf accounts to "pwn noobs" ruins ranked games.
MMR Get rid of MMR. Stop creating matches based on MMR. It's an arbitrary unfair system. Just because both teams have the same MMR doesn't mean the teams are fair. Here is an example from my plat promos:
Team A = 100 Top = 20 Mid = 15 (gold 3) Jun = 20 Bot = 20 Sup = 25
Team B = 100 Top = 20 Mid = 25 (plat 2) Jun = 20 Bot = 20 Sup = 15
As you can see, both teams have the same total MMR but B team has the advantage. Their plat 2 Katarina destroyed our gold 3 Orianna and then our nexus. I strongly believe Riot needs to do away with MMR and just match people +/- 1 of their division.