Could magic overcome, resolve or undo a disability?
Some, certainly. Assuming D&D, mid-level clerics can restore missing limbs (and, though the spell description doesn’t mention them specifically, I would argue ocular, auditory, and spinal injuries as well). So disability due to injury should at least be less common than in the real world.
Congenital issues, on the other hand, are much more difficult. Wish would work, but that’s not exactly accessible.
That said, there’s considerable potential for the magical equivalent of prostheses and other accessibility devices to be more effective than their real-world counterparts.