If you haven't seen Cabin in the Woods by now, don't read this review/analysis. What most of the critics say is that CitW is a great film with a good twist but one thing lacking is the depth of the characters. This is unusual because the writer Joss Whedon is best known for his writing of interesting and unique characters. The main group of teens that are picked off are fleshed out to the bare minimum to let the story unfold. Although it seems like a stretch, maybe they were underwritten for the very point in poking fun at the countless B-movies that have this problem, which brings me to my next point.
The teens that go to the cabin in the woods are not the protagonists. It can be argued that Sitterson and Hadley, the two men controlling the operation, are the protagonists. They had all the best lines and interactions. I read a review (not sure if it was on this site or somewhere else) that when the group almost escaped and Sitterson and Hadley struggled to close them off, they felt anxious and was rooting for them, despite the despicable plan. That's because they were the protagonists.
My second point, also a little farfetched but interesting nonetheless is that the survivors (Dana and Marty) become the antagonists towards the end. When they discover the base they let all the monsters loose, killing everyone and the biggest point to be made is that Dana kills Sitterson, practically the main hero of the story. Also think to every classic horror movie. You know the protagonist more and know practically nothing of the antagonist (in whichever form, psycho slasher, poltergeist). It is interesting to believe Whedon might have written this as subtext in the script for this very reason, but even if he didn't, that is was movies/stories are about and to have a certain interpretation of the work is interesting.
One last point which I'm sure some others might have read but I thought I'd add it anyway is the metaphor of the ending with the gods. The gods are supposed to represent the audience in the fact that we flock to the movies year after year to see crappy B-list horror movies with generic archetypes to see them die, just like how the gods demand the archetypes to be sacrificed to them. And further strengthening my reasoning that Dana and Marty are the antagonists of the story they bring about the apocalypse instead of sacrificing themselves. In a metaphorical sense them denying their sacrifice is a slap in the face to the audience in that we shouldn't want their sacrifice and we shouldn't settle for B-list boring movies.
The main point of this article was to defend some of Joss's writing and how some people say it was lacking in characters and to give a unique look on the film I hope you enjoyed it :)