Warning; Potential Spoilers.
I feel I'm the cursed child for reading that book/script. I know the reviews for the play were almost universally positive. Maybe, I could just not pick up on the pace and the feel without actors and a director.
From just reading, there was no sense of wonder. There were no exciting details of the Wizarding World, just the time-turner plot device and a number of shocking character assassinations. I don't remember any reasons to empathize, or even sympathize, or feel the slightest interest in either Albus or his circumstances. Scorpius was slightly interesting. Maybe knowing/guessing the book was a one and done story with no further development, left me expecting more...
Even the title is misleading/nonsensical. The Cursed Child. Who is the cursed child? Albus? Scorpius? Delphi? Cedric? Harry? Tom? Yes, yes, yes, yes, yes, and yes. So the title should have been The Cursed Children. Aha! The sociological/philosophical/theological point of the story! We are all cursed... we're all human...
So what is the response to the curse? Harry finally got it... humility, confession and service. Okay, but Albus needed to seriously acknowledge that even if Harry made mistakes, Albus was not absolved of his need to accept responsibility for his own life. But since, I did not like the characters, the desire for me to empathize with the story and apply this specific cure to my own curse will never happen.
Someone thought that this particular theme was not adequately covered by the continual comparisons and contrasts of the relationships of Harry-Vernon, Harry-Petunia, Harry-Dudley, Harry-Ron, Harry-Hagrid, Harry-Dumbledore, Harry-Voldemort, Ron-Percy, Percy-Arthur, James-Sirius, Harry-Sirius, Sirius-Regulus, Harry-The Ministry, Luna-Friends, Neville-Frank&Alice, Voldmort-Riddle, Lilly-Petunia, et al, ad nauseum. Parents-children-friends. The family we are given versus the family we make. The "need to forgive your parents 'cause they're only human and you'll make your own mistakes as a child, adult, and parent" theme was constant and thorough in the HP series, but someone thought we needed another one. In my opinion, this is to HP what The Force Awakens The Last Jedi is to Star Wars.
If I ever see the play, I guess I'll probably be comparing it to Oedipus Rex, Ordinary People, The Death of a Salesman (The Cursed Child might fare well), Warrior (Hardy, Edgerton, Nolte), Stand By Me....