I'm a comic book fanatic, and proud of it, so read this with that understanding.
I think, for a superhero movie, it was pretty good. It wasn't one of the best, but definitely not one of the worst. I think the main problem I had with it was Brie Larson. I think she may be the first casting in the MCU that I really just didn't like. Carol Danvers is supposed to be a fighter pilot, very type-A personality. She was written to be a strong, independent woman who takes charge and kicks butt. I don't think Larson did a good job of portraying that. For the first female lead hero in an MCU movie and the character that is considered to be the most powerful hero in the universe, I thought the movie, and Larson, failed to deliver that.
I also don't understand why they made Mar-Vell a woman. It didn't make much sense to make that change. Mar-Vell was the first Captain Marvel, and in one thread even married Ms. Marvel before she became Captain Marvel. His character is so prominent, I don't get why they changed it. It seemed like an arbitrary change that took more from the story than it gave.
Overall, I think it was a good movie, but they missed the mark on a few things. It's a bummer. I'm still excited about End-Game, but this movie almost dampened my excitement a little.