The clue was that it was made by Unbearable Films. I should have realised earlier that the film is, in fact, an hilarious take on  overlong, overblown poetry films with more pretension than meaning. 

The incongruities in the poem - that Sisyphus, the narrator, is telling us that there are no gods, there is no hell, when in fact his very being is interwoven with the necessity of their existence - serve to point the observer in the direction of this most subtle satire. Alive then skillfully extends the film beyond what even a sympathetic audience could find "bearable", sporting Sisyphus's eternal torment with bare faced irony, and subjecting his viewers to precisely Sisyphus's fate. 

Though the poor editing, unconvincing rock of damnation, and wooden acting ensured that I was veritably willing Alive's film to end, I have to say I must admire both his cleverness and his faith in his audience.