Hierarchical #cgroup is really cool. You can run systemd within docker.
While the benefits are not obvious.
Consider. being able to test / integration test large ansible playbooks that depend on ansible.builtin.service.
For those interested:
docker run --privileged --security-opt seccomp=unconfined --cgroup-parent=docker.slice --cgroupns private ...
Be sure to remove getty.target.wants in your docker image or you will drop out of your graphical session on the host.


