I have a muscle disease that makes it practically impossible to play first-person shooters. My feeling on the matter is that the amount of accommodations I would require would suck all the fun out of competitive play, despite the fact that I used to love playing Counter-Strike.
Almost no two disabilities are equal, even if they have the same name. Creating a system to set accurate handicaps for a fast-paced competitive game would be a herculean effort. There are objective measures for things like muscle weakness and blindness, but patients often don't know exactly where they rank, and these things are often changing over time.
And then there's the question of where do you draw the line between different types of disabilities? Do you throw blind people in the same match with people who have motor problems? Is being able to see enough to offset barely being able to move your arm? How are such questions resolved? How fine-grained can different pools of disabled folk get and still have enough players for matchmaking?
In my opinion, the way forward for disability friendliness is to make sure your game has a server browser and a healthy culture of community servers. Then we disabled people can organize ourselves into disability-friendly servers and answer these questions on a scale that might be feasible.
I'd also like to thank devs for creating so many awesome turn-based and non-intensive games. It took me a while to adapt, but I've learned to love many games I never would have considered before. I can still get that competitive rush from a match of chess or RISK or Backpack Battles. This kind of system would be much more feasible in a game like that.