If you will create "next gen" desktop, you will just solve some problems of already existing ones and create your own. Maturity of software is far more important, than uniqueness. GNOME didn't evolve into its current state for no reason.

Kavita, same as Komga requires too much RAM.

Komga can track ebook reading progress, by converting them to images.

Wayland is like Busybox runit. Xorg is like SystemD.

Some seem to use Debian.

IMO the closest one.

Linux Libre makes Guix unusable on most hardware. It also requires much effort to configure. Learn scheme, how to use shepherD, etc.

Not really. Void, alpine, gentoo are the only usable ones(besides non-systemd forks of arch and Debian). These are the only ones maintaining enough packages, providing enough documentation, not being just poorly maintained forks of X distro.

Openrc...

There is an example: https://www.agwa.name/blog/post/how_to_crash_systemd_in_one_tweet

The thing is that it can work. Which shown by eudev. Looks like it's important for Red Hat to make everyone dependent on SystemD suit.

See the answer on your logind statement.

Yes, systemd modules depend on systemd, that's like complaining that a GUI application depends on X.

SystemD is not modular. Logind is just an executable that depends on systemD libs. Red Hat could design it to be init-agnostic(similar to elogind). But they didn't. Any assumptions, why?