I know it has been many years since it's release, but i wasn't a potterhead then, & i want to give my opinion.
Obviously, this will contain spoilers.
Why was the-play-which-shall-not-be-named even greenlit? It sucks SO BAD. Harry is abusive & narcissistic, which the original Harry certainly WAS NOT, Cedric becomes a Death Eater & kills Neville, which he would NOT do, & Bellatrix & Voldemort have a daughter. I think i don't have to say anything else about that because it already sounds bad.
Like.. Harry didn't like his fame. He didn't like being in the spotlight, he didn't like that everybody gossiped of him, everybody wanted to talk to him, etc. Why is he signing autographs? Why is he like this? He shouldn't be!
Cedric was a loyal boy, & kind. The fact that he became a Death Eater because he lost the Triwizard Tournament is horrifying. He would NOT do that.
& imo, i think bringing Voldemort back (i know he wasn't literally brought back, but Delphini is related to him) was a bad idea. He died. Bellatrix died. There is NO way they could have made her.
To make a kid, what do you need? Love. What is the thing that Voldy can't feel? Love. He also didn't care for Bellatrix, so, how did this even happen???? Did J.K. go crazy??
Oh wait, that's right, SHE DIDN'T EVEN WRITE THE GODDAMN BOOK!
The-play-which-shall-not-be-named is just a complete disaster. I know it has a plethora of problems i didn't mention, but i didn't want to make an old testament of a post.