There are cross-platform package managers: pkgsrc and nix for example, and I believe HomeBrew runs on Linux too.
It's not that simple though as certain choices are fundamentally incompatible. In Debian packagers are expected to take "ownership" of the package, backport fixes, apply patches or fixes to integrate better with the Debian system, etc.
On Arch Linux, it will ship the latest stable version from upstream with as little modifications as possible.
You can go with one approach or you can go with the other, but you can't really do both at the same time.
Then there's the design of the tooling itself: apt behaves fundamentally different from pacman.
Some things can probably be unified here and there, but I don't think it's quite that simple.
It's not that simple though as certain choices are fundamentally incompatible. In Debian packagers are expected to take "ownership" of the package, backport fixes, apply patches or fixes to integrate better with the Debian system, etc.
On Arch Linux, it will ship the latest stable version from upstream with as little modifications as possible.
You can go with one approach or you can go with the other, but you can't really do both at the same time.
Then there's the design of the tooling itself: apt behaves fundamentally different from pacman.
Some things can probably be unified here and there, but I don't think it's quite that simple.