Systemd seems to be moving in that direction, the features are coming together to actually enable this.

Though imagining the unholy existence of an init system who's only job is to spin up containers, that can contain other inits, OS images, or whatever ..... turtles all the way down.

Docker does not set your machine up: it sets your process up.

Tech like Flatpak or Snap is closer to Docker than "machines" are — except that Docker has local, virtualized networking built-in as the IPC layer.

Okay it sets the machine up, but not the underlying host machine though.