> The biggest benefit of being a single language is massive parallelism, especially if you're process/message oriented as Smalltalk or Elixir. Most modern software, unless really pushed (e.g., game engines) still do not use all cores available.

Ummm most Smalltalks don't use all cores available, they time-slice a single OS process, aka green threads?

(Exceptions: SmalltalkMT and VisualWorks Matrix framework https://www.cincomsmalltalk.com/main/products/foundation/mat... .)

Also iirc Erlang originally did not take advantage of multi-core cpus or multiple processors for performance. The point of the massive parallelism was "process" isolation for high availability systems.