Now before you light the torches and get out the pitchforks, yelling "you can carry as a support", let me express my train of thought.
Im not talking about AP-Carry Supports in the likes of Brand, (formerly) Malzahar, Annie, Vel'koz and uhmmm....Zyra.
Its the classic enchanter Supports and Tank Supports that i have in mind.
Things like Braum,Alistair,Janna, BC, Soraka and the rest of the roster.
If you are in a low elo there is ~~most likely~~ a reason for it. You lack ~~most likely~~ in one or the other aspect of the game.
Maybe teamfighting, objective control, map awareness, cs-ing, dueling. The whole micro and macro parade.
Disclaimer: This also applies towards Supports.
The thing is, as a support player you never know which kind of ADC you will get in low elo.
Maybe she/ he is the hidden king of Kiting, but sucks at CS and chases way too hard.
Maybe he/she is a hook / skillshot magnet unable to dodge yet excells at CS, if she/he ever gets the chance to kill some minions instead of getting killed by a BC.
So where i want to go with this explanation is, that as a support in low elo you might never get a consistent performance from one ADC to the next.
Where you could easily roam after a double kill because your carry would back, now that particular marksman wants to overextend, getting the jglers attention gaining him two kills.
Maybe you could serve the former carry all the kills on a plate and he would gladly take it, as his blitzcrank butler grapped those juicy targets towards him.
In the next game you could make the best grab of the world but your carry would rather go fot the caster minions, who at least dont struggle that much with dying.
_The higher you rise the better the overall skill distribution gets_
If you make a play they follow, if you´d like to roam after pushing the wave, they will b. If you protect them in team fights, they will make kills.
Therefor id make the claim that you are way more adc-dependant in lower elo, than in higher ones.