The 3-D probably is a big factor in that. If you see the 2-D version, as I did, there are several awkward shots that call attention to themselves to really no avail. In all likelihood, these were originally intended to be seen in 3-D. Maybe this restriction cost the film some of the power that it's been known to have. The color of the film also seems really off in 2-D, and we're lucky when some parts of the film skew to look like they came out of a Stella Artois commercial, as other portions (mostly those outside of the caves) look weirdly overexposed.
I had a hard time connecting with this film. Thinking of time periods that far apart is overwhelming, like thinking about singularities and "nothingness." It's practically impossible, at least to me. I was able to imagine it a little, but probably the experience of the film is far more worthwhile if you can somehow really connect to those times.
Werner Herzog, the esteemed director of this film (though maybe not quite as much after some of the stuff he made last decade), apparently includes shots of his crew because there's not enough space to keep them outside of the frame, but at the same time he sets up another sort of documentation. The cave painters painted what they saw, cave-bears sometimes scratched on the paintings, and now we, outside of the caves, are reacting to these works. He's also interested in the layering of the caves and the stories behind the paintings themselves. Though sometimes this seems like over-reading (I'm always one for keeping things little underexposed), I still can really see what he's getting at. The layering translates in the world of today: one of the scientists interviewed in the film was in the circus before he became a scientist. These bits, and the ending that people have thought a bit strange (but which is actually entirely necessary), give the film a strong ideological weight.
The film feels far too long, and includes some unnecessary footage: essentially irrelevant footage of a"master perfumer" (put in the film seemingly as an indulgence of Herzog) and, as noted above, maybe a little too much footage of the same paintings (such as the admittedly amazing "four horses" piece). There's also a sexual bent that the film has in parts that feels a little "politely immature," if you catch me, and thus, as a result of this and a couple other things, it's a little corny. But overall, this film has you in a place you'll never, ever go, and even though this film isn't extremely substantial and isn't entirely successful, this is a more worthwhile venture than those "Italy from your living room" trips. B-