I mean, they were always able to. They just were too lazy to do it and didn't care about doing a good job enough to overcome that laziness.
"I can do it, and you didn't do it, therefore you must be lazy, because I certainly am not lazy"
What's lazy is not diving into the reasons that people may or may not do things.
Incidentally, I think it's kind of ableist to toss around the concept of ableism this lightly. Disability is a set of concrete barriers which go unacknowledged and a set of real accommodations which go unimplemented. Disability activism entails acknowledging those barriers and implementing those accommodations; it does not entail the idea that everyone is always trying their best and nobody is ever negligent.