I'm just going to be blunt and say it: I actually liked Harry Potter and the Cursed Child. Now, I know I'm one of the few that did and I'm not saying that the book was perfect, by any means. But the entire Harry Potter franchise means more to me than almost anything else. I started reading the books as a wide-eyed 5 year old and finished when I was 8. The original series drew me in and immersed me in this world that I loved and I'm glad I got to catch a glimpse into it one more time.
I'm going to try to be as spoiler free as I can, but there will be a few here and there, so just be aware of that.
So, one of the main reasons I liked the book (other than the fact that it's another Harry Potter book) is the two main characters. Albus and Scorpius were angsty and pretty complex for the book. In other words, Scorpius Malfoy is my favorite character to exist right now and must be protected at all costs. And I loved how they broke the Potter house tradition. Those are just some of the things I adored about this book.
Like I said, the Cursed Child isn't perfect at all and I can see why a lot of people hated it. It's not another novel written solely by J.K. Rowling. It's not what a lot of people expected, and it puts out weird fanfiction-y vibes at times (the train scene with the trolley lady amirite). But even with all of its faults, I found the Cursed Child to be very enjoyable and would recommend it to anyone that doesn't have super high expectations about it.