This.
I was a very early proponent of docker, and have been using it continuously since the very early versions. I read the release notes and most weeks I read the weekly email newsletter, and I still don't really have a clue where Docker is going, what its current status is (as far as how the various pieces fit together, etc) or what half the new features even do.
The docker team's communication is really poor, and their documentation seems even worse, unless I'm missing some oracle somewhere that fills in all the details that the actual documentation leaves out...