Don't agree at all
There is a reason why High MMR players do not smurf and play support heroes typically.
Hint: You have less control of the game as a support. Early? Yes you can rotate and gank etc. But even these ganks typically rely on the cores to be ready and in position. The support job is essentially to put the carries in a position to carry, after that they rely heavily on the actions of their carries.
Thus, supports rely more heavily on competent cores than a carry relies on competent supports.
stan king solely plays support and hes 8k iirc. BBB, aka Eagle, plays support a ton too and hes like 7.5
There's a few other examples, but its more the fact that playing support in pubs isnt as 'fun', so alot of pubstars dont enjoy it. Afterall, it is a game.
Infact you're just outright wrong in saying that supports have less control of the game.
In any high-level game most pubs can last hit creeps and will respond to pings. It's the support's job to make those pings mean something whehter it means lane control into chain pulls, ganks, or rotations.
FWM