This is such a silly and unrealistic argument - no one is a docker-only expert. And docker is a desirable skill, just not on its own. It's like saying that git-only experts are unemployable.
Except not really... The original article's writer doesn't know what they're talking about. If anything, knowing Docker has increased my employability in the new K8s-centric world.
1 - https://www.amazon.com/Deployment-Docker-continuous-integrat...
I tried to illustrate with some concrete examples. Like being asked about pods and ingress in interviews, which are kubernetes specific. Experience with docker doesn't help much here, gotta keep up with Kubernetes. You could de-facto fail the interview if the interviewer realizes you didn't work with kubernetes but docker alone.
Companies are super biased toward kubernetes. They're really looking for the unicorn with years of kubernetes experience in production.