A language package manager must be able to "install" the same packages over and over again (and possibly "install" multiple versions of the same package in the same environment), and the ability to push packages is generally considered part of their duty, not so for OS package managers, you don't use dpkg to send a package to debian's repositories.
> The fundamental idea of downloading a list of available options of which the user picks some, and the system pulls in dependencies, is almost exactly how dpkg and yum work.
If you reduce it to the fundamentals you don't need yum or dpkg either to do that, just a dependency solver and curl.
The fundamentals for package management also move the package into it's final resting place(s), where it's going to do it's work. Curl doesn't do that, it just gives you a single file somewhere.
I'd also consider removing a package to be a fundamental part of a manager. The two items you describe would be a 'package grabber'.
> The fundamental idea of downloading a list of available options of which the user picks some, and the system pulls in dependencies, is almost exactly how dpkg and yum work.
If you reduce it to the fundamentals you don't need yum or dpkg either to do that, just a dependency solver and curl.