Objectively, I can see why the reviews for this film aren’t that great — the spy plot is overly-convoluted and doesn’t really go anywhere, the first half of the film is nothing but a series of beautiful-but-empty shots of Theron going to a location to get information, not getting it, then going somewhere else, the trailer spends exactly as much time setting up her personal connection to the dead agent as the movie does, which is to say literally a single 5-second flashback and nothing else, the final revelation is utterly weightless, and nothing about the central mystery resolves in a satisfying way.
All that said, this film is absolutely worth seeing, for the technical qualities of the action choreography and the aesthetic of the film as a whole. Just go in realizing that the plot doesn’t really matter, and put yourself in the right mood to watch people get stabbed, garroted, and beaten to death to the accompaniment of an ’80s Greatest Hits station.