I absolutely loved the first fantastic beasts movie. Because it was not adapted from a book I thought it was a better film than the Harry Potter movies. However I left The Crimes of Grindelwald feeling confused and a bit let down. It held none of the magic of the first film and had a lot of character inconsistencies that left me confused. It's like JK Rowling was going for an Empire Strikes back darkness with her second film, but all the "mystery" she injected just didn't work together with the set up of the first film.
I think one of the big mistakes of this film was assuming that everyone knew Dumbledore and Grindelwald's backstory as told in HP and that it needed no elaboration. We go through the entire film never really learning anything about Grindelwald as a person. I really hope the next FB makes up for that.