"Healing" is an intrinsic aspect of the game that all characters can engage with (health packs, supports, shields, etc). "Metal people can't use specific abilities" is just a giant fuck you. Hey Reinhardt is too good, let's put in a hero that has a button that says literally "Fuck reinhardt" but doesn't work on Roadhog because he's not mechanical....that's the worst idea you could have. Magic Bullets have killed TCGs for years and they serve nobody. If Reinhardt is too good, alter reinhardt, or if you want a hero to counter him, do it more organically than that. For example Symmetra's orbs ignore shields, make someone with a property like that on an attack if you really think shields are a problem, etc. I use Reinhardt as the example because the person that brought the idea up did, I don't think he's too good or anything.
Just the notion of a button that does something vs Pharah/Rein/etc for an arbitrary reason yet does nothing against an organic hero, is awful. Things can be more and less useful vs certain heroes, but binary counters are not fun.