It happens to all of us, autofill. And most of us don’t like it. Queuing up for your main role and ending up with your worst role.
Originally, autofill was implemented to reduce queue times for high elo players and to make up for the support shortage. It was a necessary solution to make the new queue system work.
But later on, autofill was implemented in lower levels of play as well. It’s arguable whether it was necessary to implement it to reduce queue times, because queue times were rarely higher than five minutes. That makes being autofilled feel like an unnecessary torment.
However, there’s a thing that people often don’t notice. Due to autofill you will get your primary role much more often than your secondary role. The only price that you have to pay for it, is playing a role that you don’t know very well once every 15 games.
It’s understandable that this often goes unnoticed, since people tend to remember negative things better (getting autofilled), than positive things (getting primary role more often), but that doesn’t make it unimportant to bear in mind.
That being said, I hope you realise that autofill is more than only that thing that annoys you.