You're missing something here.
Your queue was 2 min. The queue of the people who needed a fill may have been 10 minutes.
Now, what would you prefer? To wait 10 min and then get autofilled? And so they have to wait 18min instead of 10min?
I'd guess you're slated for a turn of autofill and they'd rather get it over with than make you sit there for 10min then do it. They CAN know that it will take that long because there's a queue of ~10000 players in front of you waiting for a support and can estimate pretty consistently how long it will take to queue all of those people using supports and autofills.
I think it's right in this case. If you're going to make me wait, you better give me one of my roles. If you're just going to fill me anyways, get it over with ASAP. Roles should be first-come-first-served in these instances. If you and I are going in to the same game and one of us has to fill, whoever queued last should have to fill.