Python and Ruby are general purpose computer programing languages. Is there anything they do extremely well that erlang/elixir, can't?

From the following:

https://www.erlang.org/faq/introduction.html

    1 What is Erlang
    1.1  In a nutshell, what is Erlang?
    Erlang is a general-purpose programming language and runtime environment. 
    Erlang has built-in support for concurrency, distribution and fault tolerance.

server side computing is probably my take - it does handle more than that, eg. nerves but server side computing is the big win.