are you playing a dmg dealer and your team is retarded?
---> As unlikely as it may be you might have a chance to still carry the game.
are you playing an enchanter or cc-oriented champ and your team is retarded?
---> might as well go afk.
and this is why you can´t carry as a support. A class dependent on your partner not being ass just isn´t interesting for anyone, who cares about individual skill expression. And even if a champ with challenging cc-gameplay was added to the support roster, it would still be outshined by literally every other champ that deals good dmg, because at the of the day, when it comes to personal enjoyment, most league players tend favor damage over everything else. And I have to say even as a support main, I am in the same boat. If some asked me who I would rather want to be, the 10/2/0 rengar who stops everyone on the enemy team from enjoying the game or the 0/2/9999 rakan, who does the same shit job no matter how ahead or behind he is, the job being:"engaging and praying to god that your team is not worse than your enemy team." I would choose the catman.
but adding a more mechanically demanding support sure wouldn´t hurt, seeing how an entire support-subclass is as brain-dead and boring as it can get, with riot still trying to find ways to make them even easier to play.