I remember when auto fill was first activated at all ranks as a last resort by Riot to reduce queue times across the board.
I neither agree nor disagree with the decision Riot made.
For me, personally, auto fill is like volunteer work but for a video game. And you either do it when it is assigned to you or you skip out and take a time penalty and maybe even a small loss in LP.
It isn't exactly mandatory, but the system does incentivize you into doing it. You're guaranteed protection from the fill system for two games. Also, the fill system usually only fills a player after they've gone a good number of games either without playing support or being filled.
Some players are willing to do it. And that's fine. Most players prefer not having to wait out a timer for their next game. This means most of us can get into a game within a relatively short amount of time. So it can be argued that the system works.
I personally disagree with the sentiment that if you are neither willing nor able to play all roles that you shouldn't play the game at all. Given the vast number of complaints about feeders since the game's official launch, it seems like a minimum of 2 out of every 5 players have no idea how to play the game let alone their preferred roles and champions. But I digress.
League is nothing more than a game to me. And my personal philosophy is that a game stops being a game when it stops being fun. For me, being filled is not fun and so the game is not going to be fun for me and so I opt out and wait until I can try again if I am still in the mood.
Again, I am neither for nor against the fill system. I think the system we have now is better than the earlier seasons of pick order. But I am certainly not a fan or supporter of auto fill.