Are you confusing "can use" with "requires"?

I suspect any alternative is a fall back that cause as much troubles as it "solves". After all, the principle devs of systemd are all very much in love with dbus (bloody thing require a copy to be started by initramfs even).

You are missing the part where the user manual and the systemd new features announcement state that the Desktop Bus API is systemd-resolved's "native, fully-featured API"; and describe the GNU C library NSS API and the DNS APIs as limited functionality APIs, whose avoidance by applications is "strongly recommended" in the case of the latter.