I have long held the belief that people don't change. They can change their habits or their appearance, or they can make an improvement in their temperament and/or attitude. But ultimately, people don't change from who and what they really are at their core. Admittedly, I'm a pessimist.
This is where it is vital to be precise with words, because people do and do not change, depending on the context.
My brain is autistic. No matter what I do, and no matter how many coping mechanisms I learn/adapt/use, the way my brain perceives and processes information is never going to change.
However, as I learn, I adapt my
behaviors to employ that which I have learned. Being autistic is no excuse, for example, to intentionally mistreat others. Sometimes, miscommunications or unintentionally hurting someone is inevitable due to the differences in how NT's and ND's think, but we all learn and improve. In this sense, all people change - and they change all the time.
Some people refuse to apply what they have learned and to adapt moving forward, but that is not really anything to do with autism. That may be a personality or psychological disorder, or it could be a disability caused by brain damage.
However, most people, NT and ND, learn and change with frequency, but it is a process that doesn't always show. If I learn to crochet, then you might not notice until you get a blanket from me at Christmas. If I learn to be more diplomatic, then the change in conversation may be too subtle to notice right away.
But people don't change how they think. I know neuroplasticity is a thing, but that's more making behavioral changes over time that become second nature. Really, an autistic brain never becomes NT insofar as I know, and vice versa.
Even personalities can change slowly over time. I've got a daughter. That changed me in ways so profound I can hardly believe it myself. I'd say the changes were immediately noticeable. Other life events spark less drastic change, but it happens.