I was starting to like Captain Marvel, even with Larson's bad performance, and then the third act made her a Mary Sue and ruined everything for me.

Rating: 3/10 (9 March 2019)

I disagree with people who describe this movie as meh, mainly because this movie made me sad. There is just so much wasted potential as it is obvious that the premise itself has the works of a good story in between, but one which the movie fails to deliver.
The Story: The premise is very interesting but the main reason this movie doesn't work is the lack of tension. There is never a moment where you actually feel concerned for the well-being of the main character, and very few moments where you are concerned for the supporting characters. And even then, the tension is never allowed to build but is quickly dispelled. This is especially problematic here because this movie takes place in the past. If you remember how tensionless the action scenes with Legolas were in the Hobbit because Legolas is alive and well in LoTR, you know what I mean.
The script is poorly written which causes a lot of threads not sufficiently explored (i.e. the Kree-Skrull conflict, the nature of Captain Marvel's powers....)
You can pinpoint exactly where the movie kind off falls apart, which is the beginning of the third act. That's where Captain Marvel becomes... well a Mary Sue basically since she's infinitely powerful and has no apparent weakness. at this point you are just waiting for the movie to end because there are no stakes at this point really.
The Direction: To cut it short; bad direction. The movie doesn't have a distinct visual style, let alone one conducive of a particular mood. The line delivery of multiple actors are generally bad to the point that in some scenes I'd actually laugh and wonder how did these scenes made it into the final cut and who thought it was a good idea. The flash backs are in many cases not very well intertwined with the main timeline. The pacing however is OK.
The Acting: Virtually everyone outperforms Brie Larson in performance (Except Mar Vell), which gets distracting very early on. Larson's performance is awkward, bland, emotionless and uninspired. In fact I can't remember how many times her terrible performance turned me off while I was starting to care about Captain Marvel and her conflict.
Action and special effects: Action is pretty O.K, special effects are marvelous, just marvelous.