You joke, but it's a decent comparison. Both GNU and SystemD are projects with a bunch of miscellaneous tools with excessively strong coupling. In GNU's case that's the various userland tools relying on glibc. Both are used in the majority of Linux distros, and while there are distros without them they're not particularly mainstream. Many tools expect their options & custom ways of working, e.g. huge numbers of shell scripts are BASH-specific and need GNU coreutils instead of being portable POSIX shell scripts. Both make developers' lives easier compared to the lowest-common-denominator required by POSIX, which makes sense because POSIX is intended to be a common subset of functionality found across different UNIX OSes.

It's not a perfect equivalence, of course, SystemD diverges more from other UNIXes than GNU does.