> My main question coming out of it: if you are going to go with a dynamic language, why go with Elixir over Python or Ruby (or Clojure or Racket or ...)?

If your problem is one for which a fault tolerant, highly-scalable system with actor-model concurrency is an appropriate solution, Elixir (or Erlang) makes a good choice, and Ruby/Python/Clojure aren't particularly great choices for that. That they all happen to lack static type checking is not what is motivating the choice.

Also, Erlang/Elixir have fairly robust (for languages that are "natively" dynamic) type-checking available through dialyzer, which can be strength compared to other dynamic languages.