I can choose, "fill," but even choosing a main role, and having fill as secondary, means: "Support." I think it's reasonable to say I get support 80% of the time I have fill as my secondary role.
And I even like playing support! But I don't want to play it -all the time!!-
I liked having no prepared role, going into champ select: "do we have an ADC? No, okay, then I'll play ADC this time." Hey, I like playing mid if it's available. I'm not a very good jungler, but I'll play that if no one wants to. Oh, everyone wants one of the four main roles, sure I'll take support once in a while. . .
I like playing ADC. But I don't want to play ADC every game; and sometimes I like playing support -some of the time-
I don't want to play the same role every single game. But if I choose "fill," that just gives me support, 80% of the time! That stinks!!!
I think -everyone- should have a chance of being picked for the support role. If you're choosing fill, maybe it should be higher. But choosing fill right now, just means you're choosing support, and that's not right.