This article has been about for a while if I recall correctly, remember adoption is always optional, and in many cases your direct exposure to Docker [images] and it's perceived limitation is pretty limited. I am really liking Kubernetes at the moment and high-level concepts it embraces around container management, my exposure to Docker is limited to the image format (and Docker hub until I sort out a private registry), it's a minor implementation detail to me at this stage and none of what this article writes concerns me too much.
Evaluate docker and containers and any orchestration software in general on how it fits with your systems/values/requirements, the author talks about not being able to run his archaic insecure FTP server due to not having 15000 random ports available, right there I knew we are different people with different requirements..
In 2016 we should really be boycotting FTP if we choose to boycott free/open software...