Honestly, I can understand why people are uneasy about this. "Yes, tight coupling is being introduced in many core Linux projects, but don't worry -it's only these shiny NEW features you don't have anywhere else!"
Sounds eerily like "Embrace Extend Extinguish" redux.
Don't get me wrong, I am aware systemd is a technically superior solution. But politically, it is a trainwreck.
> Well, the very distro-specific bunch of scripts in /etc/init.d (or is it /etc/rc.d/init.d/? or /etc/rc.d? or a symlink to ...?) were some kind of tight coupling, too.
Sure, but the coupling was contained. You could still run Gnome on any distro (or on non-linux), whichever way around your init scripts were.
Say whatever you want about shell scripts, but that is not what tight coupling means.
Plus: This tight coupling did not exactly replace existing communication features. It created new ones. These are made use of.
Yes, systemd is bringing lots of new functionality. Under the hood - that is why sysadmins love or loathe it and users mostly don't care. That "tight integration" argument is mostly one that comes from people (please do not take offence, you're weighting it carefully indeed!) who bemoan that other userspace system infrastructure is left behind feature-wise. And those who love to argue about and against design decisions.