Right, it gives me the key functionality of those systems in a way that’s decoupled from the base OS, so I can just run some version of Debian for five years or however long it’s got security updates, and not have to worry about things like services I want to run needing newer versions of lots of things than some old Debian has. Major version updates of my distro, or trying to get back ported newer packages in, have historically been the biggest single source of “fuck, now nothing works and there goes my weekend” running home servers, to the point of making ROI on them not so great and making me dread trying to add or update services I was running. This approach means I can install and run just about any service at any recent-ish version without touching the state of the OS itself. The underlying tech of docker isn’t directly important to me, nor any of the other features it provides, in this context, just that it’s separate from the base OS and gives me a way to “manage packages” and run services in that decoupled manner.