I'm not going to ask you to go out of your way to read up on Avatar but trust me when I say there's scientific thought behind everything you see in Avatar. Unobtainium is actually a science fiction trope, it's name originates from a real term used by engineers to describe any rare or hard to find material that has the properties needed to fulfil a given design. An Avatar is a Human/Na'vi genetic hybrid grown in tank that is genetically keyed to its respective human controller to allow for psionic link. The film asks the question "what it means to be human" through the Jake and his Avatar, a classic science fiction question. From the human technology to the Pandoran biology everything in Avatar has had thought put into it. We got interstellar space travel, Avatars, Na'vi USB-link (queue), eywa, transferral of consciousness, cyrotanks, mechs... it's all science fiction baby. Now if you want to pretend Avatar put little effort into the science as is pure space escapism like Star Wars or Guardians of the Galaxy you're (to quote @JamesCameronScholar) patently false.