No offense, but that sounds like such a cop-out answer. There are easily cases where it is the DPS who are under-performing and can be blamed for the team’s loss. I’ve had several placement matches wherein the enemy had a Pharah and neither of my team’s DPS could handle her. Why? Because they refused to switch off of Symm/Mei/Doomfist. By the time they did switch to a hit-scan (e.g. McCree) it was already less than 30 seconds left and the objective so far in favor of the enemy that it didn’t matter.
There’s only so much a tank or even a healer can do to work on improving their game when it still comes down to the DPS playing a heavy role in doing… DPS. An Ana, Baptiste, Zen could try to heal and DPS, sure, and many do, but if the support are the ones who have to end up handling a Pharah because the DPS can’t, well, it’s not exactly “unfair” blame, is it?