Don't listen to the negative critics or the purist Harry Potter zealots.
Most of the critics that are putting this movie down want Oscar quality. Yes, critics want La La Land or The Shape of Water, while zealots want J.K. to hold their little flower leaf hands and put a smile on their wittle pouting wips.
Look, its a good movie. Does it need more character development? .. Yes. Does it need to stop building a "twist"? .. Yes. Can everything be explained during the scope of 2h 14min? .. No.
If you want to see a good movie, 4/5 stars, and addition to the Harry Potter Prequels, then this is the movie for you.