Tangentially related:
I’m severely near-sighted. Thing start blurring only 6 inches from my face and I can’t read a book or my laptop screen once I take off my glasses.
So you can imagine how horrified people are when I tell them the story of once having to drive without glasses in a minor emergency.
But here is the funny thing: I was perfectly fine. I am not actually blind - I can still see the general shapes of objects, judge distances between them and myself, see lines on the road, see if there is something human-shaped walking, see lights and what color they are, etc. The only real loss when I drove without my glasses/when I drove “blind” was that I could no longer read signs - but this route was familiar to me, so signs were not necessary for me anyway.
In a hunter-gatherer context, I would not have been useful in gathering because I could not make out enough detail to tell apart plants from each other - but I would’ve been just fine hunting. I don’t need to make out details on an animal to know that the animal is there, how far away it is, how fast it’s moving in what direction, etc.
I’m a voracious reader, most of my hobbies and profession are text-based, which is why I need glasses, and have needed glasses since I was very young.
But if I took out reading from my life, then I…would basically not need glasses at all. Almost nothing else I do day-to-day requires me to make out fine details a lot. The only other major loss is facial recognition - I can’t make out faces further than about a foot away from me. BUT, I can still recognize people by their voice, posture, behavior, etc etc.
So in a pre-literate society, I may not have even realized/noticed that I was half-blind/near-sighted, because I would be operating just fine.
I’m only (half-)blind because we live in a text-based society, where we need to distinguish fine details such as the markings of ink on paper or pixels on a screen, and recognize faces without the broader context of voice, posture, body language, etc. (re: photographs). If I did not need to do these things, I would not need glasses, and I would not be blind/visually disabled.
That is JUST for near-sighted vision, but extrapolate that idea to most other disabilities and you’ll start to see why we see it more today than in centuries and civilizations prior.