~~Linux~~ Unix since 1979: upon booting, the kernel shall run a single "init" process with unlimited permissions. Said process should be as small and simple as humanly possible and its only duty will be to spawn other, more restricted processes.

Linux since 2010: let's write an enormous, complex system(d) that does everything from launching processes to maintaining user login sessions to DNS caching to device mounting to running daemons and monitoring daemons. All we need to do is write flawless code with no security issues.

Linux since 2015: We should patch unrelated packages so they send notifications to our humongous system manager whether they're still running properly. It's totally fine to make a bridge from a process that accepts data from outside before even logging in and our absolutely secure system manager.

Excuse the cheap systemd trolling, yes, it is actually splitting into several, less-privileged processes, but I do consider the entire design unsound. Not least because it creates a single, large provider of connection points that becomes ever more difficult to replace or create alternatives to (similarly to web standard if only a single browser implementation existed).