I think anyone can change.
But I think it can take a lot of work just to get to a place where change seems even remotely possible, and a lot more hard work to keep moving toward that goal, to keep the desire alive and the dream believable.
I also think it depends on what one wants to change. A minor change requires less work and fear-facing than a major change. Major change can require many small steps that require time and support along the way.
I absolutely believe in psychotherapy!