Right, are any of the things mentioned in the GP really required if you only want this init?

I know they've attached all these projects to the systemd brand because they thought it would beneficial but it's hard not to wonder if we could avoid all those discussions if the umbrella project was called something different...

No, you can just run the systemd init system and not use any other systemd programs.

I would probably run systemd-journald just because it's really nice to have a logging system which knows about the system services, but it's not required.