This also helps with recruiting, as the tools work similarly. I didn't spend a lot of time in Rails, and decided not to go that way again, but I did appreciate that I got to recycle some of that new thinking when I started writing Node.
Phoenix also seems to be designed to recruit Rails developers. You could do worse than porting missing tools and crates from Ruby, and as far as I'm aware nobody has nominated themselves as the TJ of Elixir.
I think Elixir's big selling point is getting the BEAM runtime wrapped in a more modern language with more modern tooling. Lots of the positives people list about Elixir are due to BEAM, which you can also get in Erlang.
I was in love with Ruby and hated Java around 2009, but the latter has gotten so much better with IntelliJ IDEA, to the point where I have to admit that working with JavaFX from IntelliJ was likely my most serene programming job ever. To me, the whole ecosystem is only worthwhile because of JetBrains.
Robust IDE support for Elixir is probably a must-have requirement for many nowadays. I am really tempted by the design of Elixir and find Java/Go/C++ aesthetically repulsive, but I'll happily forget about that if I can keep my refactoring muscle memory.
It was very interesting experience being a long-time Pythonista having to be like "Isn't this awesome language with a Ruby-like syntax great???" and being told nah, let's just use async python by people who had spent years writing Ruby code.
I've written Rails professionally for almost 10 years and have been following / playing with Elixir since 2016. While Ruby / Rails are amazing and the ecosystem is well suited getting a project off the ground extremely quickly, I'm just a big Elixir fan and hope to work with it professionally one day. I'll parrot reasoning from some of the sister comments.
"having an entire environment of consistent actors, fault tolerance, hot reloading, etc is a tempting proposition." - Very tempting indeed!
"Code elegance and development joy, maybe?" - Coming from Ruby / Rails, I agree 100%
"Not being statically typed" - Again, I've worked mainly in dynamically typed languages. I've experienced typing in Javascript and wasn't the biggest fan. But don't get me wrong, Rails can be awful when trying to dig multiple objects deep to understand what the data structure of the return value is so its not completely off the hook.