I am reading several negative responses to this comment and I feel the need to throw him a hand. I like the idea of having a single place where every application is installed, to the extent possible. I like to try to install everything with apt-get, and I feel there is value in working that way.
It's way more complicated to have apt-get for some things, lein for other ones, pip install, quicklisp, the ruby gems, emacs packages, and every other environment reimplementing something that should be possible to reuse.
From the outside, and without researching a lot, it seems that the problem is that authority/responsibility is not easily delegated in the right way.
Perhaps someone can create something like a federated-containerized(contained?)-buzzword-github-like-blockchain-social-aptget-buzzword-thingie. Only half-joking here, but perhaps there's something a la git/dropbox, a product that you don't see coming until you turn the corner and They Just Got It Right. Something created on top of http://ipfs.io , for example, which looks very promising!
EDIT: Perhaps a simpler solution is to enable apt to delegate specific domains to packages marked as package managers, and have them talk through a specified protocol...