Are they so different that it’s justified to have so many different distributions? So far I guess that different package manager are the reason that divides the linux community. One may be on KDE and one on GNOME but they can use each other’s packages but usually you are bound to one manager
Any “why are there too many X’s on Linux” (where X is package manager, desktop environment, init system etc) appear to stem from the silly assumption that there happens to be an already built operating system called Linux and all these people are forking it and putting in their own stuff for the sake of their own egos and nothing else.
When really, the answer fundamentally boils down to either one of two things: either it doesn’t exist yet, or the existing solution fails to meet a need. Linux, itself, is merely a kernel; it didn’t come with a package manager or desktop environment. Those things all had to be made by separate parties and there isn’t always agreement on how best to do them.
As a Guix user, I believe the Guix package manager has advantages over “traditional” GNU/Linux package managers, as well as other so-called “universal package managers” such as Flatpak.