The language formalized and is "done". The core is written, and while it still has changes and improvements as Erlang OTP improves, the gist of the language is done (even the creator has said this, I believe).

That doesn't mean Elixir isn't a fast growing language, or that the developer mindshare is dwindling, in fact I would argue there are more developers (and new developers!) than ever. Surprisingly a lot in the Asian markets, Japan especially.

And with work being focused from the core Elixir team towards projects such as with Livebook, Nerves, and Nx for machine learning, there is a lot of valueable and cool work being done, it's just not the most flashy thing because it's so rock solid and stable.