I think that languages like Erlang, and many of the functional lanugages, show that you don't actually need shared ownership and shared mutation for a large pro

I think that languages like Erlang, and many of the functional lanugages, show that you don't actually need shared ownership and shared mutation for a large proportion of the problems out there. (Shared constant values, of course, are not a problem.) Linear typing can also help by enforcing ownership transfers between workers operating on data, allowing efficient data transfer without sharing.