The simple fact that autofill exists means that at any one point in time, there is a game that does not have 10 players within MMR ranges that fulfill all 10 positions on the map.
Look at it like jars with marbles: there are 5 jars, each with their own kind of marble, and each with an uneven number. You need two of each kind to have a complete game. It takes 35 minutes for a marble to return back to the jar to be used again. You start parting out marbles, 2 of each kind, until you run out of ones for the support position. You still have enough for all the rest though. Now, if you wait for a dedicated support marble to return back to the jar, it will take 35 minutes. Or, you could just take a marble from another jar and use that to fill the game. This means that you no longer have to wait that 35 minutes to get a marble back, and that as long as you have marbles in the other jars, you can keep making games.
Now consider that you have to wait 5 minutes before you can grab certain marbles. Either you have to wait that 5 minutes to grab that one, or you take another one. This means that the chances for all the other marbles to get filled into another position has gone up drastically.
Now replace all the marbles with people. Anytime someone decides to add a "wait time" before they get filled, your chance to be filled goes up drastically. Because no one like to be filled, they also add a timer to wait, except now theirs is 10 minutes. Now all the people that were 5 minutes also increase theirs, because their chance has gone up. This arms race of waiting keeps going until you just have your 35 minute wait time again.
Adding any kind of choice, wait time, or any other limiter to autofill just does not work. It goes against the entire point of the system. Yes, it can suck not getting to play your desired role, but the simple fact is that if you made any of these change like what is seen in this post (or the dozens of others that have similar suggestions or requests that are seen on the boards), it will get much, much worse.
