But seriously, as an anthropologist it drives me fucking crazy that people are so excited about learning Na’vi from Avatar and speaking fucking Klingon and trying to create new languages for their fantasy novel.

Actual human languages are dying because of colonialism and globalization and somehow nobody says “maybe I’ll use an actual dying language and get people excited about speaking that.” Nope, ima make some shit up and let that die. It’s ego over good and it makes me so sad.

An addendum for all the "that would be appropriation" apologists. In the late 90s as a student of linguistics, I wrote a series of essays about this topic. Part of my research was contacting elders and cultural resource professionals of various languages, many southern hemisphere, to inquire about their feelings on languages being supported by engaging in this activity. The result was near universal engagement with the idea provided people worked with them.
@terrafiedkestrel I did wonder. Still would feel rather weird to write a story about some alien race and have them speak Navajo, I think. Inventing a language seems less self-absorbed to me than claiming an existing one (that is, without talking to actual speakers about it, which is a big difference as you point out). But as a not-writer the question is purely hypothetical for me anyway.
@h5e This was much more focused on large, corporate sponsored efforts. Klingon (And Vulcan, and the Star Trek franchise in general) was relatively new at the time and given the resources involved in creating and promoting that, the belief was very clear that, given those same resources, an indigenous language could have been saved and used as Klingon (or Vulcan) with respect and consideration.
@terrafiedkestrel That would have been really cool