I would really appreciate any data that backs this up. Or is this a personal observation written as if it was a consensus? Because if we are going by personal experiences, the community definitely feels bigger and more active than before to me.
Now you may say Stackoverflow isn't a good measurement. In Tiobe Elixir hasn't made it to the top 50 https://www.tiobe.com/tiobe-index/
There is little reason for me to believe Elixir is before it's peak, the data is showing otherwise. Elixir's contemporaries (Rust / Go / Kotlin) are at a totally different place usage wise. So I tend to think this is it for Elixir, it's all down hill from here. If you have data showing otherwise please let me know.
Up until 2017 or so, you could see the Elixir community active on StackOverflow with answers from José, Chris and most maintainers. Then the community collectively moved to Elixir Forum. Wouldn’t you prefer to ask questions where the maintainers can also answer? Per the Elixir Forum stats, the number of active users keep growing.
I won’t comment on TIOBE because you can find plenty of critique elsewhere. For example, in the Redmonk rank, Elixir does fairly well on the GitHub axis, and is ahead of contemporaries like Clojure and Julia, and ahead of other functional languages like Haskell, Ocaml, Erlang, and even F#.
I strongly believe Elixir is before its peak. Elixir is most likely still growing, just not at the same pace as languages like Rust or Kotlin.
That's kinda my point. These are the languages you should compare Elixir to, the esoteric ones. Not to PHP, not to Node or not even Ruby. I doubt this is going to change much.
What I said about Elixir (lack of jobs) is also true for the languages you listed.
Now this is interesting because this counts question page views, not questions asked.
You can choose Elixir in that embedded tool, it's too bad its only for 2017-2018 but it still validates my point. My guess is the numbers for 2019-2020 are worse for Elixir.
You say the language is in decline and none of this is solid evidence that's the case. It just says Elixir devs are not really active in Stack Overflow, which anyone in the community would be able to quickly point out.