Upvoting you because we should have clear answers for these concerns. To those in the community downvoting: we should take these kinds of posts as opportunities to improve.
Elixir and Erlang are dynamic compiled languages.
The actor model being built in to the runtime offers many benefits, all of which I cannot enumerate here, but prominent among them are the ability for the VM to preemptively schedule actors, and the fact that actors are independent in memory and cannot mess with the internal state of other actors.
The jump from Elixir to Erlang or vice versa is small.
The hardest (and most rewarding) part is learning OTP and the whole BEAM runtime system, which you can do with either language.
Erlang and Elixir are slightly different syntaxes for the same semantics, and if you know one you can learn to read and probably write the other in less than a day.
It isn’t like Clojure and Java where Clojure is significantly higher level than Java in many ways. Elixir adds a few things to Erlang but is otherwise the same programming model.
> I just don't know which niche applications Elixir targets and excels at.
Pretty much any application where concurrent IO and state management are the main problems. Web applications, proxies/brokers, long running network stuff, semi-embedded low power devices that are hard to physically access and must remain reliable for years at a time, that kind of thing.
I actually agree with you that the ecosystem and tooling and especially the value proposition are confusing, and the sales pitch over the years has often been poor.
The whole BEAM community would do well to speak more plainly about the concrete benefits for programmers and companies, and the existing successful applications rather than the theoretical beauty of the syntax or the actor model.
I hope this helps.