I see a lot of people think tank is just a big damage and cd sponge, but that isn’t true at all. I don’t know where this misconception of the role comes from, but I really wish it wasn’t so believed in.
Tanks are aggressive space takers. They don’t sit around, hold your hand, and take all the enemy’s crap for you. They push in, kill things, force engagements and cooldowns, and allow their team to push forwards. Reinhard’s shield for example isn’t for his team to stand behind so they can be safe from damage, it’s for Rein to use for himself to push up without taking too much damage. To play tank effectively you have to use your resources selfishly (for the most part.)
I think most people understand that tanks aren’t meant to just be beefier DPS. Sadly, that’s what Blizzard is giving us. One Mei can control space better than most of the tank roster, and a Widow will shut down an entire sight line just by existing.
By contrast, a Rein will just stare menacingly through his shield for the 0.5 seconds it lasts, until he’s forced to hide behind a wall. And a Winston will exhaust all his cooldowns in order to tickle you a bit before you use one of the myriad movement abilities to escape. Any tank is only as good as the enemy support line allows him to be.
Tanks aren’t allowed to be tanks because, in a 5v5 environment, there just isn’t enough of them to go around. So instead they’re forced to play like a DPS, going for risky plays in an attempt to get a lucky pick.