Some DBus message is not appearing and it stalls out your boot process, finding where it was supposed to come from and why it didn't appear is a nightmare. If you want to use a different daemon than the one SystemD provides for some service it will fight you every step of the way, sometimes even undoing whatever you had to do to make the process work in a random update. As someone who experiments with weird networking stuff from time to time I've been kicked in the nuts by NetworkManager on several occasions.