Like you, I cut all ties to my (biological) parents at about the age of 21, and I never looked back. People say, "Oh, that's so sad! or "That's not right, you should patch things over with them."
Unless you have been a child in an abusive situation with selfish adults, you cannot understand the tears it causes in your psyche. I simply tell people "If there are people in your life who are miserable and miserable to you, you are better off without them, regardless of who they are." My father has passed and my mother has made overtures since--dangles of scraps of her beloved money. 30 years, and she still believes she can buy my attention.