It was demonstrated by engaging people in the mythology, just like at Expedition Everest. Themed entertainment is not a text book, it is not all spelled out. There are plenty of fictional animals, but there is one common strain through all of those chosen by the creative team that dreamed up the park. No aliens, no purely fictional creatures, no animals just made up for the park. All of the animals chosen are rooted in cultural understandings of the world: folklore, myth, legend; not contemporary story telling. Years of research and work go into a park. It was no accident that aliens were never part of the plan until chosen by financial executives.
Rhoda's career is dominated by an obsession with research into places and topics, so much so though Disney decided that the best way to tease Pandora at the D23 Expo was to pretend that he had taken Imagineers on another research trip. Science fiction is just not the sort of thing Rohde has done in his career as a creative leader. You can't actually visit Pandora or do more than just talk to James Cameron, and as cools that may be it is not the same as trekking across the Himalayas to put research a fictional creature (to understand its cultural origins).
No purely fictional creatures? Fanstasia? Bugs Life? Festival of the Lion King? How are those not fictional? How are those not contemporary storytelling?
The more you post, the more it's obvious that this is your opinion based in very little fact.
Let me drops something else on you. The original intent of the park was that the three areas were to be cordoned off. The northern section of the park for animals that are, Dinoland for were, and Beastly Kingdom for never will be. That was dropped when Beastly Kingdom fell through. It's a simple theme. "Animals that were, are, and never will be". There's none of this existential buffoonery you're assigning to it.
It doesn't mean that Avatar fits or doesn't.
I'm not saying one way or another. What I am saying is this nitpicking that you are doing about Beastly Kingdom being the European mythological demonstration of humans interaction with nature isn't supported by the facts we have. It's not even supported by the mythological creatures that were chosen.
What I'm telling you is what I was trained on first hand by people passionate about the park and it's message at a time when Camp Minnie Mickey was still seen as a placeholder for Beastly Kingdom. You can either accept the information that I'm giving you as is, or you can continue to ignore it and proceed on this imaginative tirade where there is a deep significance that require leaps in logic.
With that said, we are going around in circles, so I'm out. This was fun.