In a world where we often work by targeting containers, and also often use tools like Carton, I don't see a big advantage to growing the core distribution. In fact I see doing so as being disadvantageous to the container paradigm. A nice slim distribution, with simple means of either bundling or pulling down what is needed makes more sense, I think.

To some degree I think that the existence in the core of modules that aren't needed for building and installing Perl and installing modules is mostly a result of inertia and a desire to maintain backward compatibility. I don't know if Hash::Util is used by the Perl install process, or to facilitate installing other modules. If not, maybe it's a candidate for exclusion from the core, except that we're kind of locked in to avoiding breaking changes. CGI was dropped from the core not only because it wasn't needed there, but because keeping it seemed like an endorsement of an antiquated programming model.