Aren't you being a little too harsh? The Dockerfile automates the installation of libvirt and custom components to launch the VM so while the title might be misleading it is hardly "not adding" anything.
Docker is not adding anything whatsoever. The "dockerfile" could be converted with a simple macro into a plain bash script and it would literally be the same thing. The container is not abstracting anything here; you are using KVM of the host system.
You even have to install more packages in the host than in the container.
You could even just run the original script the Dockerfile is wrapping directly which will even autoinstall the packages for you.
Yes, Docker is effectively acting as the supervisor process for this container, only managing its process lifecycle and allowing easy removal/persistence.
My (linux) desktop has a macOS icon on it. I click on it. That starts a QEMU/KVM process which runs macOS. When I quit out of that, it is gone. When I click on it again, it runs again.
I suppose there are a few files floating around that persist between runs, and are not utterly trivial to manage. Just ... trivial to manage.
You even have to install more packages in the host than in the container.
You could even just run the original script the Dockerfile is wrapping directly which will even autoinstall the packages for you.