It's worth noting that co-writer/director Neill Blomkamp sets District 9's pivotal event — the arrival of a derelict alien spacecraft over Johannesburg, South Africa, leaving more than a million extraterrestrial refugees — in the 1980s. Apparently, that's when the filmmaker learned everything he needed to know about allegorical/satirical science-fiction.
Blomkamp sets the bulk of the narrative 20 years after the aliens' arrival. A heavily patrolled slum has sprung up around the hovering mothership, and the creatures — given the derogatory nickname "Prawns" because of their arthropod-like appearance — have become the object of hostile native sentiment. Casually racist government bureaucrat Wikus van der Merwe (Sharlto Copley) gets a promotion that means overseeing a mass relocation of the Prawns to a new ghetto farther away from the city. Unfortunately, a run-in with an alien liquid leaves Wikus facing a particularly ironic transformation and forces him to become friendlier with one of the Prawns than he ever thought possible.
Yes, South African cinema is attempting to use metaphor to purge its apartheid guilt, while also providing a convenient counterpart for Americans as we confront our feelings about unwanted immigrants. Blomkamp serves up clunky analogues for real problems of segregation — e.g. threatening graffiti, police brutality, the Prawns getting high on cat food — and hopes you're either sympathetic enough to the themes not to care or too wrapped up in the exploding bodies to notice.
What's most disappointing about District 9, though, is how familiar it all is — provided you look back a generation. It's refreshing that Blompkamp takes a fairly matter-of-fact approach to the aliens' presence on earth — there's very little by way of dramatic re-creation of humanity's first contact with alien life — and he quickly dispenses with the familiar approach of hiding the look of his creatures as long as possible. But the alien-as-target-of-racism angle was covered by 1988's Alien Nation, Wikus' fate looks remarkably similar to that of Jeff Goldblum in 1986's The Fly, and the grudging, mutual-need-driven bonding between human and alien hearkens back to Enemy Mine. Throw in nods to Aliens and RoboCop in other sub-plots, and you can see clearly that Blomkamp did his homework re-watching the best of that era.
Which is an entirely different thing from re-creating it. Employing that popular modern device of fake-documentary/found footage — though only when convenient, it seems — Blomkamp tries to work around the lack of a sympathetic protagonist by spending a lot of time on interviews with experts, friends, etc. He's trying to say something insightful, it seems, about governmental policies and corporate greed that result in divisiveness and hatred, but everything he has to say sounds like something you've heard so many times before that it has become feel-good background noise — "We Are the World" rendered as Muzak.
Mostly, though, he's left with as much shooting as he can work into the final hour, and he works a lot of shooting into that final hour. The result is a moderately entertaining slice of sci-fi action that doesn't really work as an idea-driven drama. In coupling genre pleasures with satire and message-mongering, Blompkamp is just a couple of decades too late to the party.