I think you mean Erlang there and not Elixir. Elixir itself is only 10 years old, Erlang is 35. That said, Elixir does seem to be pretty stable, I've not run into major issues when learning it with regard to dated material being "wrong" (either actually wrong with regard to the current language incarnation, incomplete like pre-`go mod` golang materials, or "off" from the current idiomatic use of the language).