I like how they're saying that Docker's strength is in letting you never learn how to package applications. Which is a bit like saying that a Google self-driving car's strength is that you never have to learn how to drive.
The useful features of Docker are resource isolation, image layering, and staged deployment. The idea that you can run two versions of PHP or move your files between distros has been a solved problem for at least 30 years.
I'd go even farther and say that the main useful feature of docker is the image layering. Even the resource isolation has been available with LXC and cgroups for a while now.
But docker certainly has a nice way of letting you use all these features in a friendly package. It's often not the most original things that are the most groundbreaking, sometimes it's when something comes along and takes all the parts you already have and puts them all together in a useful way.
The useful features of Docker are resource isolation, image layering, and staged deployment. The idea that you can run two versions of PHP or move your files between distros has been a solved problem for at least 30 years.