Haha, I didn't really like the movie, plot-wise and with the character development. But there topic does seem to point something to think about.

I think the statement,
"But the Na'vi are also very physically capable, obviously very intelligent, aware of their global environment, well-nourished, healthy, omnivorous, adaptive, and even inventive.

They have domesticated animals, are troubled by few serious natural predators, can live in different environments, have easy access to many varied natural resources (for sustenance and building/making), and can travel and therefore communicate over long distances (dozens if not hundreds of miles a day on their winged animals).

And most importantly, the Na'vi have regular and intimate access to a moon-sized supercomputer -- a neural net supercomputer at that -- that connects them to every other living thing on their world and have had such access for what could be millennia."

would explain it the most. Its like today, our way of living evolved throughus adapting. Like tools last time were created in order to make life more convienient. Or a better example would be a computer is needed to process data but the more data is needed to be processed, the RAM is it needs to be upgraded. So for the Na'vi tribe, we could say that they already have quite a lot of convieniences or are already confortable with their lifestyle. Also with that, their culture may also be helping to soften any other inconvieniences they have. Just saying only, haha.