OP does say system software, and although Erlang can have amazing uptime, I'm not so sure about it's raw performance story (on the other hand, I do remember seeing some insane benchmarks from a elixir framework, so, maybe I'm wrong).

Also, other than Erlang and Elixir, which other reasonably mainstream language has this as first class features? Even Rust doesn't really put queues and message passing front and center, it just makes it easier to get away with doing traditional thread programming.

Things can be old in years since discovery/invention, but still in it's infancy in usability and adoption.