I enjoyed reading your perspective and it does relate to things I've reflected on with respect to my own parents.
I would say that some take advantage of their role (maybe and probably without even knowing it) in believing parenting comes with a hierarchical role. In doing so, they create an imbalance in the parent-child relationship. Recovering from this I think is difficult unless a parent is able to reflect on and see the imbalance they've created.
I think parent-child relationships need to be made on equal ground where both the parent and the child have equal value in and of themselves. With such an approach I think a parent could still instill values and create boundaries in the relationship. However, from such an approach both parent and child would be participating equally in a relationship that would continue to unfold throughout their lives.
Think about it this way... would anyone want to be in a hierarchical friendship where one friend was a taker and the other friend had to give everything to support the existence of the relationship? Probably not. As an adult, I would say that when the parent-child relationship remains hierarchical then it might just be time to limit that relationship in your life. This, in practice, would probably be easier said then done because, after all, they are still family.