Well, to be honest I'm not fully sure. I've never been able to fully contend with the idea of ableism. There are certain ideas in the category which are easy to agree to, like that "ugly laws" are bad (that was a real thing, look it up).
But, you know, a person with a disability is literally less abled in some way than an otherwise person. So unlike racism, like, reality itself is basically ableist? I'm sure what people mean is that ableism is the socially constructed parts of disability, but it's definitely more complicated because it's not entirely reducible to what's socially constructed.
In any case, you're walking down a pretty unnerving path if you try and make any claim about the worth of a person based on their abilities. Which is weird, because, again, like we know positive economics will suggest people with disabilities cost more to hire, so they'll often have a hard time finding employment or will earn less. And I think most would want to think of this as ableist, but that seems unlikely to effect behavior without costly interventions.
I think most would say that everyone has equal worth in some metaphysical sense not tied to any function of reality.. it's just that this seems to bear almost no weight on how people objectively act in regards to ability. At best we have a few laws to help people with disability function in society, but I don't think we're ever going to see full fair treatment of disability unless we get fully automated communism or something.
In any case, I think it's pretty clear that superhero films don't really care about ableism much unless it's the overt kind people will get mad about, but the medium still has a kind of inherent ableism to it.