Most of us have long standing childhood issues with our parents. Most of us learn to deal with it as we get older or after we have kids. Not all of us. My husband has disowned his entire family because of the sh*tty parenting they did. My parents are fine-ish, but I'm better living 500 miles away from them.
A lot of people go to therapy to deal with this.
Your parents sound pretty s*cky. Like super fake and won't deal with real issues. That's why they seem nice, but if they really wanted the best for you, they would have done something about it. No decent parent would have let this slip by. You can't do anything now, and you've done *wonderful* in your adult life making up for it.
Maybe write them a letter and flat out tell them what they did? I for one have told my mom what a horrible mom she was. Yes, we still talk, and still have the same relationship I've had with her since I can remember. It's never been close, but at least it's still there. But I'm the kind of person who tells people what I really think of them, to their face.
All I can do is not repeat the same mistakes with my daughter. I have "let go" so much with time and distance.