Dynamic Que Vs Other Sports
Allowing premades and non in the same queue is like having a High School Basketball team in the same league as a pickup game team. It's just really hard to balance out and I think that is what peoples complaint is. They look at it and don't believe that they have the same chance of winning as the team with the premade.
Riot talks a lot about growing the sport and people finding friends. The problem is people play one game with each other than never see each other again. To continue with the sports analogy when you are a kid playing a sport you end up playing with the same kids every week because of geography. Eventually you make friends by being forced to interact with the same people over and over.
My thought is this. If there was a better system for meeting and making friends online through league, like a premade team matchmaking system, than people wouldn't be complaining. They would all have a premade group with similar interests and availability for ranked and they would enjoy the game more as they make new friends.