I saw it last night with a friend half my age who didn't like it either. What follows is a slightly franker version of what I posted to imdb. I don't think it has any plot spoilers (that would be impossible as the plot is a retread of the 'evil technos on innocent savages' theme), but I refer to peculiarities of the movie:

In some ways this movie is trying to be an adult version of Ferngully
The Last Rainforest. The part of the world inhabited by these
creatures, the 'moldy h icans' is like a director's wet dream of Eden,
only with attractively plant draped mountains that float (instead of bolting into
space). Meanwhile the inhabitants are a wide range of large or
stretched versions of creatures we are familiar with: Big big bugs or
flying reptiles.

It is a concept flick- man through technology transmits mind into
fabricated creature that can live among the intelligent kind of its
homeworld. The homeworld has something we (evil humans) want. Humans cannot live on
planet but we want a precious material which defies gravity, baldly
called unobtainium. The aliens are blue, and look (pick one) like
elongated supermodels (every one of them) or cat people with no fur or
whiskers. Either way you get wide faces and big yellow eyes right off
those 70s paintings on black velvet. I forgot to mention pouty lips.
Somewhere there must be a sociologists thesis on what are the elements
of face and body type that denote attractiveness while deforming other
characteristics. The one possibly somewhat original idea is that the
intelligent social aliens have tails, at the end of which are exposed
nerve fibers that can bond with significantly useful critters to ride,
such as a reptilian eyed large flyer, or other critters where the nerve
endings might come from other parts of their bodies like a tail to head
mind-meld.

I do not recall any of these sharp toothed creatures eating or any
significant blood flow from anything. Even the roots of the trees are
nerve endings according to the Sigourney Weaver character. Meanwhile,
there are no latrines, these natives apparently wander around the
vertical environment making nerve contact with wondrous beings but
don't need to eat, shit, raise children, set broken bones, sign
contracts, clear leafmold, or establish a government. They don't
apparently make music unless they are all arrayed in a large pattern
helping the roots save someone's life or convert them to alienhood.
It's like woodstock without the rain, the mud, or for that matter, the
music. The movie soundtrack was by James Horner who seemed to channel
tangerine dream at times, and John Williams at other times. So
sometimes the music was spacy, and other times it was starwars.

It goes on for 2 and a half hours and is excruciatingly unbelievable on
its own terms. More than the ten bucks, it's the 2 and a half hours
I'll never get back and the pained look I could feel on my face as the
bad guys were made to look really bad, driving bulldozers ten stories
high or trying to destroy an especially important part of the fiber
tree of life.

If you loved the self-righteous extermination of the environment to
make a point such as "On Dangerous Ground" where the good guys blow up
an arctic oil refinery in order to promote environmentalism, this film
may resonate with you.

Personally, I think putting the ten dollars to a meal with a lot of
fiber in it would have had more agreeable results with a better end
product.