Nah I'd say when there is a similar skill match up the tanks decide how hard you loose but not your chances at winning. If your tank isn't actively throwing you still have a good chance of winning, but the amount of abilit supports have to 1. Make a terrible to ok tank play into something that can win a team figth 2. The amount of impact you have in games where someone isn't actively throwing is crazy.

The amount of times on support where I have had a tank or dps effectively feeding and being able to use a cooldown or make plays that turns said feed into a acceptable or game winning play is crazy. Case and point the last game I had on ana our DIVa was diving in 1v6 in a room, and would have died in 99% of cases and by just throwing 1 nade and hitting 1 sleep we won that team fight. Playing tank recently often feels extreamly dependant on the your team, like you can't push forward cus your supports chose the wrong pick for the map or can't hit any healing us crazy.

Not saying support is op but there is no way they are still underpowerd/low impact.