"Cube" was trying desperately hard to be absurdist and Kafka-esque with its setting that is pure symbolism and no realism. ("Ooooh I get it. The cube is society!") So, when they find out that the exit room was the very room in which they started, and that their entire struggle to extricate themselves from the cube has been pointless, the point is, in fact, that it was all pointless! ("Ooooh I get it. The cube is society!")

Over and over again, people (most notably the character who was one of the designers of the cube that they are trapped in) give long, symbolic speeches about what the cube is, why it exists, etc, etc. Essentially, it was created by thousands of people, all working independently, who had no idea what purpose their small role had in the grander scheme things. It's kind of an anti-conspiracy theory: instead of a single organization masterminding all of the world's problems, the point of this movie is that there is no evil mastermind but instead of bunch of obedient schmoes just doin' their jobs that inadvertently create a massive, lethal, inescapable prison of labyrinthine futility. ("Ooooh, I get it. The cube is society!")

The symbolism is so heavy handed; the Ionesco/Albee/Kafka influence, so bombastic. This is what makes the movie a dog and gets it only one turkey. It tried very hard to be arty and profound and failed badly. And, as the other reviews have rightly attested, the acting, dialogue, characterization, special effects, and just about everything else were incredibly weak.

Response From RinkWorks:

So you're saying, what? The cube is society?