I'm not going to compare it to the original MIB because that would be unfair as it is a new, separate movie.
The movie was just bearable because of Tessa Thompson's and Chris Hemsworth's chemistry and acting. But that's it. Everything else about it was lackluster.
I could spot the villain in the movie right when he was introduced. Now, cliches and tropes aren't always bad, but it should take a bit more effort to find the big plot twist.
The humor fell short half the time. I couldn't stand the Pawny character. His jabs at Agent H were funny the first couple of times, but then it just became boring and overused. In the end, he was just annoying.
The biggest problem I had was the character development, or should I say the lack of it. Throughout the entire movie, the only one who changed was a side character. Spoiler Alert from here on out! When we first see Agent H, he is careless and irresponsible. At the end of the movie, he is never shown being responsible the way he should be. He somehow ends up being the main leader of the London Branch. And I guess you could blame it on the fact that he's had his memory erased and that's the root of his problems, but it still doesn't change the fact that he is never shown any responsibility to take up the mantle. I was really hoping that he'd give the position to Agent C and say that he wasn't ready for it. But he didn't. He literally took the offer. Can't wait to see how the London branch functions with him in charge.
As for Agent M, she starts off as this know-it-all that just wants a chance to prove she could be a MIB agent. She does things she thinks is right. At the end of the movie, she's still exactly the same. She literally had no character development what so ever.
The movie can be fun! If you're not paying too much attention. The bad guy aliens were pretty cool too. But all-in-all, this movie was just so disappointing.