Comment by galcerte

Unlike PulseAudio, dbus, and other userland components, it is perfectly possible to have a Linux system which works with most software without systemd. runit and OpenRC are two of the most popular init alternatives, which are just inits, and nothing else, unlike systemd. You might argue you have to use logind and udev, but that has been spun off into elogind and eudev. There is also seatd as an alternative to elogind, which is quite big itself.