> Systemd is turning "init" into a framework of ...

This is conflating the systemd project and they systemd init system. Most of the things you mention are seperate systems (systemd-resolved,logind, polkit, etc.) that are part of the systemd project and interoperate with the systemd init system, but are not part of the init system itself.

Agreed and the conflation is somewhat intentional. When you install a system, you get all of that. Custom kickstart files can strip away some of it. For the longest time, you would get polkit regardless. The rpm spec file was changed about a year or two ago so that it can be removed if someone did not exclude it specifically. To be fair, each OS maintainer is including or excluding bits of systemd in the default configurations, so that is not entirely systemd's responsibility. Every year systemd appears to be subsuming more and more system functionality.

Is it correct to even say that systemd "brought" cgroups and lxc? They seem like fairly independent projects.

systemd did bring them mainstream, but yea cgroups were around for years before systemd was a thing. But they were mostly independently managed by some small daemons that did things based off rules and other things like that mostly. Systemd changed how they got used, primarily because multiple management systems working with them tends to cause issues, but using them for low impact isolation and tracking of daemons automatically really turned them from something you'd independently setup to something that brings a lot of utility for just about every use-case everywhere.

You can still use cgroups independently with systemd, but it's recommended that you use a service and the delegate option to have systemd create a cgroup hierarchy and also know that it shouldn't mess with it after creating it. This lets you have your cake and eat it too if you have a case that systemd doesn't handle (I'm working on a setup with this myself for a coding sandbox setup).

I think Docker had a bigger influence on cgroup use than systemd.

I disagree because everybody who uses Ubuntu is using systemd, but only a fraction of them use docker.

Ubuntu uses snaps heavily bringing cgroups to play.

I agree with you and edited my wording.