So I think this movie would have a 6,5/10, maybe a bit higher if they actually do the sequels right.
The twist at the end is really weird... and they are going to have to do quite a lot of explaining to have it not conflict with the old books/movies... unless it was a misdirection and Grindelwald is just a liar... but that would be even worse to be honest. The plot definitely had some issues. But I liked the feeling of the movie. It felt like everything was more mature, and there seems to be a decent amount of world building going on compared to the original movies, which limited themselves to Hogwarts mostly.
The best thing about this movie are definitely the main character and antagonist. I like Newt Scamander, he is very different from Harry Potter... he seems to have more of a personality. He is competent, but also kind of awkward, and I think that is an interesting thing for a main character to be. I believe the actor that plays him said he believed Newt has Aspergers, I can definitely see that in him too... it is a fresh breath from Harry Potter... and most main characters in children movies. The same can be said for the villain. Grindelwald is a better villain than Voldemort. While of course I love Voldemort more for nostalgia reasons... and Voldemort definitely looks less... stupid... Grindelwald does not appear cartoonishly evil. Don't get me wrong, he does something truly horrible pretty early on, he is definitely not a good guy. But Voldemort was just pure evil, he visibly enjoyed torture and murder and did not really pretend to be good. Grindelwald makes some convincing arguments and you can really see why people would follow him. Of course, his arguments may just be a way of recruiting people... I don't know if he actually believes in any of the things he said himself. Still I like that they tried to make him a little bit "grey", Grindelwald's speech/vision was definitely the best scene in the movie for me.
{Spoiler}I especially found the World War II and atomic bomb vision he showed very interesting. He is kind of right, "muggles" are about to develop weapons that could destroy the world. It makes complete sense for wizards to want to intervene before that happens. What does not make sense is that immediately after showing why muggles are dangerous and need to be controlled, Grindelwald tries to create nuclear-level destruction himself by trying to burn down Paris for some reason... Maybe that was meant to show Grindelwald is a hypocrite, but I would have preferred for him to not do that.
Having said that, I absolutely despise the "Quennie" character. She is annoying and her entire role in the movie is pointless and... well weird. Her decisions are not believable.
{Spoiler}I get why other people would join Grindelwald. But Grindelwald tried to have her sister murdered in the last movie, and he clearly doesn't think too highly of muggles, even if he doesn't want to kill them all. I don't see why she would fall for this... It makes no sense at all.
Also the reason Dumbledore refused to fight Grindelwald was stupid.
{Spoiler}They made a "bloocpact" to never fight? And the bloodpact is somehow a physical object? How did that happen. Their friendship ended in a fight involving Dumbledore's brother, which resulted in the death of Dumbledore's sister. Did they make a pact after that? That seems ridiculous. If they made it before did Dumbledore fight WITH Grindelwald against his brother? If that were the case his brother would have died pretty quickly. I get that they have to come up with an excuse for Dumbledore to not intervene directly, because they want to drag this out for 5 movies... but it is heavily implied that Dumbledore was in love with Grindelwald. Couldn't they just use that as a reason? Dumbledore being reluctant to fight his former friend/love interest makes perfect sense. No need to come up with a stupid solution to that problem. Also, why is Grindelwald even worried about Dumbledore if this bloodpact exists? Also why the hell does he keep that item on him if it is so important?
Anyway I liked the LeStrange story... The two flashbacks were well done. I also think Flamel showing up made sense. He lived in Paris and was a friend of Dumbledore. So I don't feel like they just shoehorned him in. It made perfect sense for the story. But Nagini... Why? Did Voldemort's pet snake really need a tragic backstory like that? This is really weird if you think about it. Dumbledore interacted with the woman that would later become Voldemort's snake. Couldn't it just have been a random snake? Or a person who never interacted with any of the main characters before becoming a snake? I don't know... they are forcing it a bit too much. (I don't consider any of this to be a spoiler since it is in the trailer).
So yeah, I am interesting in seeing where this is going. I would love to see World War II in the Harry Potter world. I also hope we get to see Voldemort at some point (they can totally do that, because Voldemort studied at Hogwarts somewhere during this time). I wonder what they will do with the next two movies. The last is obviously going to be in 1945 because that is when Grindelwald is finally defeated. But how are they going to deal with that 18 year time jump? Will they recast the main characters? The flashback from Halfblood Prince actually takes place before 1945, and Dumbledore looks much older there... Also, since the first movie took place in America and the second in France... could one of the follow ups actually take place in Nazi-Germany? That would be so weird and interesting to see.
Anyway I enjoyed the movie. Even if I didn't like all of it, I was not bored or annoying by it. It isn't a masterpiece but it is many levels above Last Jedi. Which reminds me...
{Spoiler}If this had been Last Jedi in the final scene Grindelwald would just have told Credence: "Your family is irrelevant, they were a bunch of drunk muggle criminals and they died. It doesn't matter." So I guess we should be happy with what we got, because that would have been stupid.
Definitely go see it if you get the chance. I don't think it was as bad as the reviews would have you believe.