Programming languages are technologies typically optimized for a specific purpose - jack-of-all-trades technologies tend to not do anything particularly well, they are just “good enough” for some people. So if you are working with anything that has a reasonably wide scope you are usually committed to working with multiple technologies and that can mean multiple (specialized) programming languages.
Now, I know that someone will say “Erlang isn’t technically an implementation of actors”. That’s fine, but it’s close enough.
That doesn’t change that you yourself may be too fixated on the Actor model (the same way an OO enthusiast may focus on objects, totally overlooking the “messages”).
The BEAM doesn’t care about the Actor model - it’s about lightweight processes and how the BEAM schedulers manage them. For me this talk expresses the spirit of the BEAM most clearly:
Lambda Days 2015 - Torben Hoffmann - Thinking like an Erlanger
The BEAM is more than a virtual machine - it’s actually more like a mini-OS - one that is smarter about how to get the most (concurrency, rather than raw power) out of the host hardware than the actual OS it is operating on.
Complaining about Elixir, Erlang or any other BEAM langauge not being good enough for all applications is almost like complaining that bash, bourne shell, zsh, etc. aren’t good enough for all applications. The concurrency support means that you can choreograph or orchestrate concurrent activities fairly easily while at the same time being able to “outsource” certain work to other tools that may be more suited for a particular task.
Now some developers don’t want to leave the “comfort and familiarity” of their preferred programming language/environment - but that is a separate issue (and an unreasonable expectation in our increasingly “connected” world).
So competing implementations of the Actor model are largely irrelevant because the real gold is with the BEAM’s schedulers (and to a certain degree “distribution” but more from a local fault tolerance perspective rather than “heterogenous” and “world-wide” distribution).