> simply having the ability to pull up a replica of almost any *nix environment on my laptop

Umm, I struggle with that. I have Ubuntu machines that run in production. They are VMs that run systemd for some stuff and Docker containers for others. The only way to (easily) replicate such machines on my laptop is via VMs (e.g., Vagrant + VMware), not via Docker only.

I do use Docker a lot... Inside VMs.