That's true to some extent, but I think the real reason for the coupling is because that's just IBM's use-case and worldview. Cockpit is essentialy a wrapper over systemd commands, and one commentor has demonstrated how it could have been envisioned as a modular platform allowing end-users to wrap anything from direct kernel interfaces to entirely custom commands. They've made something useful and beautiful, but I wish it had been designed to make less assumption about it's runtime environment and expose it's toolkit to end-users so that we could all enjoy it for our own needs.
Any predecessor to cockpit like webmin or cpanel have always been a huge mess, because there is no uniformity in Linux.
Dbus is a message bus for all of Linux, this is a requirement if you want to develop stable tools. A uniform message bus so you don't have to keep changing your code for every single distro and release.
