Systemd is in the images. Even if you could not run the containers sucessfully, the containers started and when systemd started in the container, that affected your host. It is a known issue with Systemd. Running systemd in Docker containers is tricky, but if you want to test Ansible without creating huge virtual machines, that is a way to reduce required storage size s well as CPU and memory requirements. Otherwise you could not test Ansible tasks that would install packages that require systemd.
https://docs.docker.com/engine/daemon/#configure-the-data-directory-location
When the containerd image store is enabled (as it is in newly installed Dockr versions), the bigger data is not in the docker data root, so the documentation also explains how you can configure containerd.
I’m not sure what you mean, but it looks like a Docker installation issue we could discuss further in a new topic. Docker Compose is just a plugin to use as a client which will not remove features. Maybe you mean not every parameter is supported in compose, but almost all are. We are happy to help you with that as well, but I recommend keeping this topic for the Dive into Ansible guide issue.