Doesn't really affect me as I will play just about any role.
I suspect that their might have been a feedback loop when Riot tried to implement, auto fill protection. Since more people are protected, more people are needed to fill the gaps. That in mind, it should promote support/fill options a little bit, simply to get that protection, so it seems like a creative solution. That in mind, I keep hearing stories about people losing that protection just because someone dodged. And that is kinda problematic, cause people are getting cheated out of the system when that happens.
The other issue is that Riot had separated Flex Q from Solo/Duo. Dividing the player base like that, is probably the other reason why Auto fill is enabled.