Nah. it's the adc damage atm. Jinx is able to more or less survive forever, have the highest move speed in the game, and mete out the most damage, on an almost purely auto attack basis. Don't watch what adcs do in lane. Watch what they do once they begin to roam. Jinx will poke the crap out of the entire opposing team until a play can be made, and there's not much they can do about it except try to flank/ambush, which doesn't go very well if she has a team.
She's basically the best pure auto attacker in the game, and they put her on steroids (Vayne's primary damage is all in Tumble, which is why she didn't get affected too much by the nerfs). As long as Jinx has high attack speed and Orb, 90% of champs can't zone her post lane. if they get within 700-820 range a countdown begins toward their death. And then Jinx gets 275% Movement speed, and then everyone else dies too. She doesn't even gain much from speed boosts from supports except very early game.
Jinx is like Draven. In lane, if you give her 1-2 kills, she'll take a mile. That's enough to set her purchase curve into a winning damage kit. She could be the crappiest adc player in the world, and she will still go 16/0 if you give her those first 2 kills (I Know; I've done it, and I suck at adc).
And..... Most supports do not have infinite Mana spam. Although they have ways to recover it, they often bottom out, and some quicker than others. If Sona is spamming skills to proc
it takes about 8 skills to put her in low Mana jeopardy and then she basically has to sit back and wait. Same with Nami. They do consume.
However, they thrive on builds like this:
That's a mana battery (and might be becoming even stronger soon with an upcoming Manaflow Band rework). But it takes awhile to get to this build, and most supports don't build it. If the supports go
I guarantee you can punish that, because that build doesn't speed up adcs much, doesn't actually transfer a lot to the Support's Damage/Heals (They think they do but AP beats them every time) and keeps the support slow as well, meaning you can take them out.