There are holes in the movie, but here’s what they tell you in the film:
Fixing a spinal cord CAN be done. But it costs a bundle and the VA in 2154 won’t cover it. The hero’s _brother_ is the guy who was originally supposed to go Pandora to “drive” his very own (human) DNA/Na’vi DNA hybrid/clone. (VERY expensive! More expensive than a spinal cord repair.) But brother is killed on the street before he can ship to Pandora. His identical twin, Jake (the movie’s hero), is induced to step in as driver after being discharged from the Marines.
Jake agrees to the gig as a challenge, he’ll be doing something he knows how to do (basically being a body guard for the teams that interact with the Navi) and because he’ll get a decent bonus for stepping into his brothers shoes—otherwise the clone is a complete loss of time (it’s a six year passage to Pandora on a sub-light cryo-ship), money, and resources, because the Avatar can only be driven by an individual with an identical twin-type DNA match.
Once on Pandora and he’s quizzed by the Colonel, who admires his moxie for taking on such a big job and promises him that his spinal injury will be repaired if he gives him all the intel he gathers about the Na’vi. From there, the movie really takes off
...So the whole spinal cord thing is covered by “the VA won’t pay for it.” But it can be done and it’s dangled as a prize in front of Jake for doing what he’s told to do on Pandora.
I agree that the film takes some not-so-subtle swipes at the Bush, business, and the American military But...it’s still pretty amazing. You root for Jake. He’s a likeable guy who wants to do what’s right. And he takes some big gambles in the film. Some pay out. Some don’t.
In films like this, the military enlisted man (sometimes junior officer) is trotted out as a well meaning and likable person but ultimately a dupe and a pawn of larger and sinister forces embodied by Col. Quartich and the evil yuppie.
I am reminded of how the soldiers are portrayed in the vomitus that is Lions for Lambs, likable and well meaning but the movie practically screams....CHUMPS.
I really wasn't concerned about the holes in the story as much as the parts that were completely filled in.
Also, nice how in the future the VA is still screwing over the troops.