I read anything and everything to find answers to my issues. I have that book, and I have related it to all my toxic relationships, both with my parents and others. Perhaps they are like me, and, searching for answers.
No matter how right parents think they are, and how they have done everything right there are issues they cannot see, cannot accept. Does that make them a bad parents, no, it just means we all make mistakes and we all need to grow, to do better.
Perhaps you should read the book and not take just the presentation of the book as a negative.