The point is that beyond some basic typing things, programs written in Erlang, Elixir, and Gleam will all have the same core structure. Immutable data plus pattern matching plus BEAM processes has a pretty strong affect on any BEAM language.
I dunno... Scala, Clojure, and Groovy users? Small user bases, but the languages are not dead.
I find the opposite more troubling, actually. Take the C# ecosystem and see how there's one de-facto application framework (.NET), one logging lib, one etc... It's usually Microsoft's way or the highway, and 3rd party libraries and frameworks struggle to get any adoption. Consequently, that ecosystem is much smaller, less diverse, and less innovative.