Having seen the film (for free at an advance screening. I won't give Oliver Stone any of my money) I would have to say that the real reason the film is a failure is that it terrible. It is lousy in every way, bad story, bad script, incredibly bad acting (Angelina Jolie), lousy CGI, bad directing, bad editing, unfollowable battle scenes, too long, too boring, and about people you definitely don't want to spend three hours of your life with. This is one of the worst movies I have ever seen.
Having seen the film opening night, I fully agree with you EXCEPT, while Angela was definitely acting over the top, at least she had a personality and might herself have conquered the world. The worst performance in the film full of bad performances was Colin Farrell who never showed an ounce of charisma, certainty, charm, confidence, let alone exultation in battle or conquest. If he was a confident queer, I could have liked the movie. But not a petulant, weeping indecisive dweeb who never seemed to enjoy anything.