My point was not to defend Docker, but to suggest that Docker is increasingly irrelevant to the broader ecosystem.

I wouldn't use Vagrant because I (like many people) always target an orchestrator and not hypervisor or bare metal.

I use Docker as a nigh-universal package repository and package manager, with a huge and up-to-date selection of packages. It gives me a consistent way to run daemons my software depends on, nearly everywhere, including pinning the version and ensuring they all use the same config. It's docker-hub, really, that provides most of the value I get from Docker on a day-to-day basis, and that's the part I'd miss. I know there are other ways to create images and run containers, but I almost never create—or even modify—them myself.