Indeed, as you noticed the networking setup is primitive, but for the time being it works for us. Currently, the hub is chosen to be as reliable as possible and nodes at the end of the spokes are prepared for hub down (ie. they stop safely ).

Kubernetes is more than just Docker containers. Having managed small computing clusters for a decade using custom scripts I find that the value of K8s is how easy it is to manage highly complex applications over an array of loosely connected computing nodes. So in my view k8s includes networking, orchestration and principles of how everything should be done and managed to achieve redundancy, performance and stability.

Containers are just a convenience for simple deployment on asymmetric nodes and is only part of K8s.