Why not make Autofill optional?

It was, it's called "Fill." No one used it hence "Autofill."

people honestly can't be this dense

Because then it wouldn't be Autofill. It also wouldn't solve the problem that autofill helps to solve, which is the different amounts of players queueing for each role.

bumped so fast.

Not actually autofill, and does not solve supp shortage, and now possible ADC shortage.