I mean, how many classic worthy blockbusters are there each year?
I think Avatar is at least on par with a lot of the MCU films, and a lot better than stuff like Transformers, Pirates, the DCEU films that are not WW etc.
If I compare it to 2017 blockbusters I have seen: In terms of quality, Avatar destroys King Arthur, Ghost in the Shell, XxX 2, Alien Covenant, Valarian, The Mummy. It is also better than Fate of the Furious and Beauty and the Beast. It is also not (much) worse than Kong, Guardian 2, Wonder Woman, Spidey, and Life (I count Avatar roughly amongst this category in terms of quality). Dunkirk, Logan, and Apes are the ones this year that are (significantly) better than Avatar.
I am not saying Avatar is in the upper tier of best blockbusters of all time, but I think it is a very competent and enjoyable film. I really enjoyed the visual aspects (not many cgi-heavy films pull this off nearly as well, not even today), thought the worldbuilding itself was great, and the actors did good, despite portraying clichéd characters.
Unobtainium. They're fighting over a resource called Unobtainium.
It doesn't get much lower than that.
It is a term used by scientists and science media in the real world, given the context in the film it is not out of the question for us humans to actually call it that. I agree it doesn't really sound good, but it is not nearly as dumb as people are making it out to be.