None of these are mandatory though. It's up to the distros whether to use them. For example at this point resolved is pretty commonly enabled by default, networkd not at all, and timesyncd is perhaps 50-50 with chrony.
The most convincing advocacy I have seen for systemd (by a BSD developer, its fairly well known) is that it provides an extra layer of the OS (on top of the kernel) to standardise things.
I don't see how it defeats the point - it still nice init / services manager, it still provide features say sysvinit couldn't do at all for my _services_ and management/lifecycle of services.
How often I tackle with resolved or networkd or timesyncd - not even sure, may be once a 2-3 months, while systemd-as-service-manager I do almost every day.
Mind providing some example on your setup/cases?
It's a new (ill specified, non standard) runtime to target. It's like what Win32 is to the raw NTDLL, or the dotnet or Java API. It hides the OS.
systemd (the PID 1), journald and udev are different, though, because they're mandatory; and there's no alternative to logind while technically optional.
Really curious now what it was so.