Riots take on Autofill, however, they are tackling it from the wrong angle.
The issue isn't that people are troll picking when they are autofilled, the issue is that, that person doesn't feel comfortable at all on that role. In the scenarios I have had with champ select that someone was very angry that they got autofilled, they didn't troll pick, they just wished the could switch with someone or cry out that they are terrible at the position that they got filled in.
Imagine this, a person Queues up for ADC and Mid lane, they get Autofilled to Jungler. They barely play Jungle. Now on the other side of the Queue, the opposing team has someone who is a Jungle main, and is pretty experienced at what they are doing.
End result? It's obvious.
The more experienced Jungle will out class that Autofilled person. Why?
The more experienced Jungler will know timings better, better predicts when the Autofilled person is going to be at a certain camp as they are more likely to run a standard route to play it safe, they are better at smiting (Securing objectives), they are better at counter banking through certain bushes and more effective at map pressure overall.
This goes for every other role when you are Autofilled and the opposing team has a person who mains that role.
All this does is create a disadvantage for one team, when in fact the game is suppose to be as close to 50/50 as possible in terms of skill and rank, not RNG that you're not going to get one of the positions you are good at.
I do however agree with Riot, champion select trolls are a pain and need to be dealt with, however, the overall picture of someone getting stuck on to a roll that they are not comfortable is a much more dire issue.