It's funny that no one seems to even consider using the distro package manager when it's time to complain about Python package management again. The deployment environment is usually well-known thus scriptable, and developers can be expected to know how to install packages on their own distros. And, of course, if the package is deployed as part of a distro, everything is taken care of by the distro people.

Flatpak is somewhere in the middle because it can and does centrally update dependencies, though they are packaged in larger boxes and it's tempting to include more exotic stuff in the app package instead of creating and maintaining a separate Flatpak shared with other dependees.