In the words of my friend after we walked out of the theater, "I enjoyed most of the stuff that didn't have to do with Dumbledore, Credence, or Grindelwald."
Seriously, the plot is so messy, and there are so many points that could be removed with no effect on the overall "story." Several characters from the previous two films just go completely missing with little to no explanation why, and no, I'm not talking about the switch from Johnny to Mads. On the other hand, supporting characters from the first two films are thrown into the spotlight, and new characters are shoehorned in to fill screen time but not actually accomplish anything. The 3rd film in a series is too late to introduce new main characters, folks.
We get recycled storylines and plot elements that have been done better in other films. As other reviews have mentioned, the original canon has been completely tossed out the window, adding to the heap of distracting, confusing, nonsensical things in this movie.
The canonical magic system has been trampled in favor "pew pew" fights, instead of creative battles using the beloved spells from the books. It looks like we'll have to keep waiting for the epic duel between Dumbledore and Grindelwald teased in the books, because it certainly doesn't happen in this movie.
Overall it was just so disappointing to have a 2.5 hour long movie filled with so much nothing, especially after the first two enjoyable, albeit jumbled, movies.