The strength from having a reusable medium (docker or otherwise) is when there are integrations on top to manage deployment, failover, DNS, load balancing, certificates, etc... none of which is handled by docker. You must have noticed since you had to implement some of these.

Kubernetes is getting adoption because it's helping with that. That's where the hard work and the value is.

Docker by itself is not notable, it's a fancy zip/rpm file.