You seem to believe that your parents owe you something. That you being back home in your 40s is their fault.
It's not, and it's not a helpful way to look at it. From the outside; they're letting you live there. That's huge.
My parents were never going to leave me anything but anxiety and trauma, which I've carried along with a spinal disability from an early beating for my whole life. I was homeless at 13, in a Salvation Army near the only job I could get at 17, and had to bounce around and do a lot of jobs I'd rather not have done, and live in a lot of places I'd rather not have lived. There was no fallback plan for me, though. Nobody to go home to, and there's little value or point in assigning blame.
I'm nearly in my mid-30s now and I own a house, have a son and earn above the national average by a decent distance. I'm also only just learning to drive, but again, that's life sometimes. Some people get driving lessons and a car for their 17th birthday, some people get a room in a Salvation Army.
You'll waste the rest of your life tantrumming about what happened before if you're not careful, and that's what you're really angry about.
For what it's worth, I think they were probably ill-advised to sell the flat - but it was theirs, not yours, and so all you can do is have an opinion and then move on.