It's always tempting when a film doesn't work to blame the writers, and there's no way of telling which ideas Jon Spaihts and Damon Lindelof contributed, and no denying that either way, they were acting at the behest of Scott. But while we're reluctant to point fingers, there's no denying that the finished product of "Prometheus" is a mess, script-wise, and that most of the film's crippling flaws come from that. While it raises intriguing ideas, they're mostly underwritten, undefined and undercooked, confusing ambiguity with profundity in a way that's undeniably reminiscent of the worst of Lindelof's "Lost" (a show on which Lindelof recently said he had no real desire to explain the mythology of, which certainly carries over). The dialogue is pretty patchy throughout, character motivations are dictated by plot rather than human (or robot) behavior, and subplots stack up without really being followed through. But most crucially, there's simply too many unanswered questions, and not in a "What's that intriguing space jockey creature" from the original "Alien" kind of way, but in a "the filmmakers don't care enough about this being coherent" kind of way. What exactly is David up to when he spikes Charlie's drink with the black goo? Is the plan to smuggle back the alien life form in Shaw's belly, as suggested by David when he tries to put her back to sleep? But how could he know that they'd have sex and conceive? And how did he know what effect the goo would have? And why isn't this made clear? There's a difference between building up a mystery and just being aggravatingly withholding, and all too often the "Prometheus" script ends up being the latter.
2. Third act turns into dumb action-adventure at the expense of the ideas
Only worsening the script problems is the way that the film abandons most of its thoughtfulness as it drops into the third act and becomes a dumb-as-a-rock sci-fi horror that feels like it could have been directed by Paul W.S. Anderson. Throughout the film, there's the sense that the spectacle is being shoe-horned in (what's the point of the storm sequence, exactly, other than to provide a few money shots and to give a reason to separate Fifield and Millburn from the rest?). But it only gets worse in the third act, best demonstrated by the attack by a mutated Millburn on... well, some people we've never seen before, pretty much. There's no stakes, because his victims are essentially strangers. It feels out of nowhere, because last time we saw the character, his helmet was melting over his face, which seemed to be the definitive end of him. It feels dumb of the characters to open the door with open arms to him, when they've already had to put down one mutant in the shape of Holloway. The make-up design makes him look like an extra from "Ghosts of Mars." And the overwhelming feel is that it exists only because it's been ten minutes since the last action scene. And it continues on -- the confrontation with the Engineer is rushed, scrappy and vague, and while the spaceship collision is a nice hero moment for Idris Elba and his crew (and actually motivated by character and plot, for once), what follows is disappointing. Charlize Theron is kept alive for no reason (what was she going to do on the surface, exactly, except wait for die?) other than to be given one of the more unintentionally hilarious deaths in screen history, squished like an ant under the plummeting Engineer craft. And that the surviving Engineer (who's survived... how, exactly?) then stalks Shaw, who he's basically never met before... just to be a dick? It's entirely possible to be a tentpole that deals with big ideas, but when the third act is as stupid as the one here, the spectacle and the food for thought simply cancel each other out.
Here's the thing about prequels: most of the time, we simply do not give a shit. We don't really want to know how Anakin Skywalker went from annoying moppet to Darth Vader. We're particularly uninterested in how Father Merrick first came across demons. And we have no desire to see how Robin Hood became Robin Hood in Scott's last film, "Robin Hood." They invariably hurt the mystique and integrity of the earlier films, and that's certainly true here. Part of the reason that the Alien was so terrifying was that it embodied the unknowable -- a seemingly impossible-looking creature that seemed to want nothing but to kill everything, that couldn't be reasoned with. That was frightening. Knowing that it's the grandchild of the girl with the dragon tattoo only lessens one of cinema's most iconic monsters, rather than enriching it. Being a prequel also lessens the suspense; we know that there's no chance that the engineer will make it to Earth with its payload of black goo urns, because we know from future Alien movies that Earth is still alive and kicking a hundred years into the future, so the outcome's never in doubt.
4. Disappointing design of the Space Jockeys
For the most part, the design work is stunning (although again, the old prequel trick of more advanced technology in the 'past' is glossed over). But there's one fairly major disappointment, which is the look of the Engineers themselves. Scott has been open that the question of the enormous, helmeted 'space jockey' scene in the original "Alien" provided inspiration for the new movie. And yet it's hard not to be disappointed when those elephantine helmets come off to reveal... a giant, bald, albino Vin Diesel-looking motherfucker. We get that they should be vaguely humanoid if they sacrifice themselves to serve as our creators, as the opening scene suggests (although surely we should look exactly like them, if that's the case?), but any hint of them being truly alien is lost, and sheer size aside, they're not particularly menacing. Maybe they'd have served as a testosterone-y prequel to "Dark City," but it's hard not to feel deflated by the solution to that particular mystery.
One of the benefits of the original film was that rich supporting cast, with a bevy of character actors like Ian Holm, John Hurt, Yaphet Kotto and Harry Dean Stanton, they brought depth to the crew of the Nostromo. Here, despite a fine cast... not so much. Of the more notable figures (and there's plenty of redshirts knocking around purely to get killed off late on), Sean Harris' Fifield, the world's least likely geologist, is wildly inconsistent, Rafe Spall's Millburn is mainly kind of annoying (and never convincing as a scientist) and Kate Dickie's Ford has literally no characteristics of any kind. it doesn't help that Scott's eye for casting is off, particularly when it comes to nationality: why are Brits Idris Elba and Rafe Spall given ropey American accents, while American Patrick Wilson and Australian Guy Pearce dodgy British ones. Even Shaw herself goes from an English-accented child to a Swedish-accented adult). And what's curious is how much even the bigger cast members seem adrift, in part because they're often inessential to the story. Logan Marshall-Green is charismatic, but doesn't have a lot to do before he gets mutated: we get that he's arrogant, and disappointed that he doesn't find what he's looking for after two hours of looking around a cave, but there's not much to the character beyond that. Charlize Theron's mostly given one note to play (other than her beguiling scene with Idris Elba, maybe our favorite one in the film), with a daddy-doesn't-love me arc that's obvious to even the dimmest audience member from the first reel. And just when Guy Pearce is revealed to be on the ship (and why exactly does he feel the need to hide? Dude's a trillionaire, he can pretty much do what he wants on his ship, surely?), he's quickly dispatched. And lord knows what Patrick Wilson's doing in the film -- we assuming there's more on the cutting room floor, but even so, it's the biggest waste of a good actor since Danny Huston stood around the background of "Clash of the Titans."