I'd also like to add that accessibility is not a binary that's either on or off. Parent comment might be thinking of features for people with high disability ratings, but eventually everyone has some level of disability. Some even start of life with one: color blindness, vision impairment. Most people have progressive near vision loss (presbyopia) as they age.

Also, disability may not be permanent. I recently underwent major surgery and for at least a few days afterwards using my cell phone was nearly impossible. I resorted voice control a few times because I did not have the coordination or cognitive function to type. (Aside: cell phones in general are accessibility dumpster fires, but it took a major life event to demonstrate to me how bad it really is.)

So no, accessibility is not just a toggle switch or installable library. In fact, I hope future UI design incorporates some kind of non-intrusive learning and adaptability, such that when the system detects the user continually making certain kinds of errors, the UI will adapt to help.