There is many kinds of disabilities, and some heroes are more accessible to some than others. I’ve discussed this matter so much since game launch from all players that advocate to remove Symmetra autolock, and despite I’m not being disabled myself, I know most of the arguments on this.
Mercy: Guardian Angel requires some hard turns to be properly used, and some kinds of disabilities make those movements hard to execute. Plus, Angelic Descent requires holding an extra button while moving in the air, and some disabilities prevent you pushing so many buttons at once.
Reinhardt: Random muscle spasms can make you turn your shield in unintended directions in the heat of a fight, leaving your team wide open when you don’t want to. Firestrike is also an ability that for optimal Reinhardt gameplay need to be used constantly, and that require aim (even if loose).
Torbjörn: Requires aim. His turret is too weak for him to rely solely on Turret and armor packs. Torb needs to deal damage with his gun to be effective, and use turret as complementary DPS. So, any disability that prevents precise hand motions will not make Torb viable.
Winston: His tesla cannon don’t require aim, but his leaps do. And making effective use of Primal Range also involves a lot of quick movements and frantic leaps. Both are out of range for certain disabilities.
Moira: The problem is Fade. Same reason as Winston. Other than Fade, she is accessible, but I bet you will not want a Moira in your team that never Fade to escape hectic situations.