Docker isn't perfect, but you can't argue with the fact the container ecosystem was rather stagnant until recently.

For years I knew of openvz (weird? needs custom kernel? supported?) and lxc(seems to be low level? how do I get started?) and just used xen/kvm on servers and virtualbox/vagrant locally.

It's funny when Bryan Cantrill talks about how solaris+zones had solid containers years ago.. and he is right, but the end user UX was abysmal [1].

And then docker comes along and shows...

That this can work:

  $ docker run -t -i --rm centos:7 /bin/bash
  [root@2214e639debe /]#

That building containers can be easy using Dockerfiles instead of 'make random changes to this container and then clone it forever'

That with a few cli options you can have persistent volumes and locked down networking.

So, sure, docker may have some issues. In a year we may all be using rkt or rocker or who knows what. But for now, docker is here and people are using it for things.

[1] I ran opensolaris at home for a few years. I think I only ever made 2 zones. I never got patching to work and either had to choose between sparse zone that wouldn't work right or a gigantic full zone that I couldn't manage to patch.