I think smalltalk and erlang are so interesting because they model the idea of small computers so differently.
Lisp just feels like the purest way to understand what the units of a programming language really is.
I have written a fair amount of Elixir (and targeting business applications) and I think Elixir's expressiveness lends itself well to making more abstract models of the business processes and data seen in solving business problems. However, writing Elixir I find you end up reading a lot of Erlang and in certain problem spaces I could imagine the appeal over Elixir. I could absolutely see where if I were writing more technically oriented programs.... programs closer to the hardware in some ways or programs designed to communicate with other programs (protocols, etc.) I could see Erlang as being a more clear and direct language in these circumstances.
All of this is very hand-wavy, but it's my impression.
Last time I touched Erlang, "Learn you some Erlang for great good!" was fresh out of the printers.
I've just not had time to learn further. As swapping between languages when trying to complete my original Tcl project is tricky. I'm now poking around with Crystal.
A rookie example of erlang and converting strings to base16. I posted in haste a while ago on Tcl's IRC but fun. Never did implement the teddy bear colour.
Other than that, vanilla Erlang is THE way to go.