The movie fails because it presents antagonistic forces that proceed from different sources, and, for this reason, confuses the viewer. It would be like a movie in which blonde women were being killed by a serial killer-AND lightning strikes.
Can't you just feel the air coming out of the balloon? The movie presents a micro-organistic foe but, at the same time, another foe, a god figure the appears as a deer standing on hind legs. All of this appears to proceed from the characters' discovery of an ancient ruin that they have partially uncovered in a typical archaeological dig. Some of the characters appear to die from this microorganism, but some appear to be seduced to their end by the god/deer. Which foe are we to fear and follow? It almost seems as though, part-way through the script, the writer found a single antagonist too simple or unsupportable and felt the need to come up with another, a sidekick of sorts. It does not work.
The effect, as I suggested earlier, is a diffusion of focus, resulting in the viewer's caring less and less about EACH foe, as weird as that sounds. If you let the helium out of the balloon, it sinks to the ground, and no one will want to watch it.