The author mentions coupling with kubernetes due to config maps and such. That is certainly a risk, but if you use environment variables for config (which IMHO you should) then k8s makes it trivial to just map your ConfigMap to Environment Variables.
I've got a few apps running in k8s and none of them know anything about k8s. If avoiding coupling with k8s is what you want (and I agree it's the way to go) then it really isn't that bad. The hard part is not knowing what you don't know.
I think the real question then is why are people running apps that need to be k8s-aware at all? K8s already provides a number of primitives to solve many problems without reinventing the wheel and going "cloud-native" within the application. There should be a very strong reason for any need to access the api directly.
I've got a few apps running in k8s and none of them know anything about k8s. If avoiding coupling with k8s is what you want (and I agree it's the way to go) then it really isn't that bad. The hard part is not knowing what you don't know.