I'm not sure how much you know about Elixir, so apologies for stating anything obvious.
* Elixir sits on top of the BEAM (the Erlang VM), which has several decades of being battle tested.
* Elixir is at its core a functional language, with immutable only (not just by default) data, and comes with built-in processes and OTP, a library that provides ready-made abstractions on top of processes. It's very, very good at concurrency.
* Elixir has Mix, Hex, and ExUnit, which provide great tooling and package management.
* Elixir's ecosystem is rather vibrant and active. Phoenix, LiveView, Livebook, Nx, Axon, and more. Elixir generally takes the approach of building things on top of Elixir from scratch, which frees it from having to deal with impedeance mismatches. See Livebook (the Elixir notebook solution) and Nx/Axon, and all the other machine learning stuff going on in Elixir right now.
I highly recommend the presentation The Soul of Erlang And Elixir by Sasa Juric.
I can’t answer every question known to man based off the vague prompt I answered. I took a pretty good stab at it. :) I also don’t know what makes things learning worthwhile to every type of person.
> Do Elixir's ideas improve your thinking when working on other languages?
Most languages do, and I’ve already mentioned Elixir’s unique features. Although, in a way, it will make working with other languages feel painful if you do any concurrency. Elixir and Erlang change the way you think about and work with concurrent processes and do it in about the best way possible, as it’s built in to the language in a core way. Learning how to deal with immutable data, writing pattern matching code, and functional programming are also all pluses.
> Are Elixir developers in demand compared to other languages?
I don’t know how to judge this, because define demand. The answer is ultimately relatively irrelevant to me and how I look for positions. If you’re asking, in a roundabout way, whether there are well-paying jobs in Elixir, the answer is yes.
> Is it a fad language?
I don’t know what a fad language is. Stack Overflow is not the global truth, and the plot is linked without context. Elixir has had its official forum for seven years now. It was created around the beginning of 2016, which roughly corresponds to the peak in the data you posted with a bit of lag in the downturn, as might be expected as people learn of the new forum.
Lastly, making a decision based upon what is popular now is not a long term thinking decision. What is popular now was making head winds 10-20 years ago.
* Elixir sits on top of the BEAM (the Erlang VM), which has several decades of being battle tested.
* Elixir is at its core a functional language, with immutable only (not just by default) data, and comes with built-in processes and OTP, a library that provides ready-made abstractions on top of processes. It's very, very good at concurrency.
* Elixir has Mix, Hex, and ExUnit, which provide great tooling and package management.
* Elixir's ecosystem is rather vibrant and active. Phoenix, LiveView, Livebook, Nx, Axon, and more. Elixir generally takes the approach of building things on top of Elixir from scratch, which frees it from having to deal with impedeance mismatches. See Livebook (the Elixir notebook solution) and Nx/Axon, and all the other machine learning stuff going on in Elixir right now.
I highly recommend the presentation The Soul of Erlang And Elixir by Sasa Juric.
https://www.youtube.com/watch?v=JvBT4XBdoUE
It really gets at the core of what makes Elixir and Erlang special, but I'd say Elixir has a lot more quality of life improvements over Erlang.