This is what we call The Law of "The Adventures of Tintin": When your faithful animal sidekick -- in this case dog/frog thing Woola -- is the most compelling character in the film, you might have a problem. It's not like Stanton didn't assemble a strong cast, at least in places. Taylor Kitsch and Lynn Collins can act, clearly. But they're not exactly scintillating screen presences -- they're fairly bland, and Kitsch seems too contemporary for the post-Civil War setting: Tim Riggins in a hat and beard. And the rest of the cast aren't given much to play with either. Mark Strong, Dominic West, Willem Dafoe, Ciaran Hinds, Thomas Haden Church, Samantha Morton, are all wonderful scene-stealing actors, all of whom never really get any material worth sinking their teeth into. Strong, for instance, has played bad-guys far more compelling than this one. Perhaps the only actor to truly make an impression is (of all people) James Purefoy, who is charismatic and funny in his couple of scenes. However, he is the rare exception because for the most part, the characters of "John Carter" are largely indistinguishable with little to set them apart. Instead, the only joy and true entertainment one really finds in “John Carter” is the charming and cuddly Woola acting like a silly old dog that just wants to play and be around his master. That’s great and all, but not so hot when we're missing that level of energy and engagement from the hero of the movie.
In part, the problem with not caring about the characters comes down to not knowing an awful lot about them, or indeed the world. Despite the gratuitous (but frequently necessary) expository dialogue, almost no one is fleshed out in any consistent or compelling way. It’s a reasonable expectation for the film to provide, if not backstory, then at least some insight into the behavior of major characters, but all we get are scraps, and often in the wrong places: Samantha Morton’s Sola, for instance, a side-character of little significance, gets a whole arc to herself, whereas we never really learn why Dominic West's bent on conquering Barsoom, or why Mark Strong is manipulating him, beyond them both being dicks. Any motivation they're given you could plug them into any film and the shadowy alliance of evil at the heart of it could justify their means. With Carter himself, it's not like the writers had a lot to work with -- Rice Burroughs deliberately keeps Carter's background oblique. But in a way, that would have been preferable to the thin, and generic, backstory we get: a dead wife and child, something that essentially turns the character into Jonah Hex.
That we don't get much to care about in terms of the characters is mainly due to there being so much damn plot to get through. Stanton, Andrews and Chabon combined aspects of the first two Burroughs novels, "The Princess of Mars" and "The Gods Of Mars," but the plot is essentially their own invention, and it's curiously uninvolving from the very first scene of Mark Strong appearing to Dominic West. Why are the red Martians fighting the other red Martians? What's the relationship between the red Martians and the Tharks? What's the geography of the planet? (Look at "Game of Thrones" for a way to demonstrate this stuff relatively easily?) Where do that second band of Tharks, that Carter slaughters single-handedly, figure in? And for newcomers to the property, there's an intimidating amount of terminology: we know we thought that half of the characters were called "Jeddark" before we worked out that it meant "king." Assuming that's what it means. Say what you like about George Lucas, but at least the early "Star Wars" films had a relatively simple good vs. evil tale, and managed to drip-feed the weird terms and concepts, rather than throwing it all at you in the first five minutes.
Think of the sequence where John Carter comes up with against a race of bloodthirsty Thark monsters (even though this same race was his ally – as we said, we're still a little confused on this). We see Carter hack and slash his way through piles of multi-limbed alien beasts and at one point Stanton makes the decision to drop the sound effects, pump up Michael Giacchino's appropriately overwrought score, and cuts in between the Martian slaughter to a flashback sequence of Carter finding his wife and child dead. This is one of the only let-loose action sequences in the film, and we're already cutting away. Unlike his former Pixar colleague Brad Bird in "Mission: Impossible – Ghost Protocol," Stanton seems incapable of building action sequences that build on top of one another, compounding tension and stakes. Instead, John Carter jumps around a lot. So to have this moment, which actually has the possibility of soaring aloft holy-shit-this-is-cool action, to be threaded with such morose material, well, it ends up being something of a buzz kill. Imagine a triumphant scene in "Avatar" undercut by the tragic back story of how Worthington lost the use of his legs, and you'll get the idea. Plus, you have no idea what is going on in this melee. You would think, coming from animation, Stanton would place an emphasis on geographic and motivational transparency. We need to know what he's doing and what he's up against. Instead, Stanton cuts around the action, either to the flashback or to slow motion shots of Carter swinging a sword around or howling wildly. It may seem cool, but it doesn't do anything for the audience. We can't be let in if we can't make out what's happening. And it's true of most of the other action sequences as well, which tend to be both brief and confusing.