I think there is a major difference between having a big possibly over-complicated application program in userspace, and putting something like that in a critical spot in the system itself.
If your application program has a flaw, it's probably not a huge deal. Maybe it crashes occasionally. You save often, you have autosave, it's not a big deal.
But a system component that can crash the system, render it unbootable, hand control to a hostile third party, etc - it's much more important in that case to keep things clean and proper to keep the machine itself stable.
Part of the disconnect between the Sysd cabal and the traditionalists here is about what we mean by the machine. We are often running linux on bare metal as our workstation. From what I have been told, they typically run it in virtual machines on server farms instead, and use Apple workstations. So from their point of view, it is just another application, and it shouldnt be a big deal to restart it occasionally - especially after they put so much work into improving boot times. But from our point of view, we dont care much about fast boot times, we want a stable system that doesnt need to be rebooted all the time.