gnome hard depends on systemd, so much that for it, *bsd (and any non-systemd unix-like) had to write a systemd-shim to emulate some functions of it, and/or gut some of systemd's components such as logind in to elogind
Not for a while now; accountsservice runs fine with cosolekit. I still don't understand why the broader Linux ecosystem burned the better part of a decade on the long-solved problem of "who is logged in to this TTY?", but whatever floats their boat...