Wasn't my favourite. I actually began falling asleep in the theatre. The biggest issue for me was that I felt there wasn't enough humour and light, as in literal brightness on screen, to ease the tension. The Harry Potter films and even the first fantastic beasts films did a good job of adding humour and bright scenes to contrast the darker tones of the films.
As many have said, the film was quite dark (brightness) and I found it to be very quiet as well- all around it made it fairly difficult to follow; combine that with the jumpy story line and I found it a bit hard to get invested in the story.
I didn't really mind the jumpy story-telling itself, because the whole plan to get to Grindelwald was that no one would know exactly what was going on, so it made sense that the audience wouldn't have known exactly what was going on. But- and I could be wrong- it seemed as though Dumbledore did know what was going on the entire time... I don't know, felt like a bit of a plot hole. Also, Dumbledore is in the title of the film but we don't really see him that much. Shoulve been called "fantastic beasts and the magizoologist who goes far beyond his job description to thwart a dictator."
It felt like the film didn't know which way to lean - more into the magical lore or more into realistic politics. I felt both fell flat. If you're going to make it more political, lean into it entirely. Make Grindelwald a villain due to his manipulative persona, his ability to convince people to do his bidding without magic - ya know, like real world villains.
The confrontation with Grindelwald at the end of the film fell flat - he just let the election be taken away from him, and people who supported Grindelwald just let it happen as well. I was expecting him to rally the crowds into riots, to fight them before they were able to have the election go through properly. Idk, take from real world examples of extremists - it doesn't matter what the facts are, their ideologies are "right" in their minds and they defend it at the expense of themselves and others around them.
Lastly, a lot of the film was telling rather than showing. Dumbledore said several times that he had been in love with Grindelwald, but we never see it - same with Ariana's death, we never get to see it. I think Ariana's death would have been a fantastic opportunity to showcase the malicious side of Grindelwald, like he could've egged on the confrontation or even done something to harm Ariana in the confusion of the fight.
Anyway, I have hope for the next one!