I don't agree with this; that's one of the things you can do with it for sure, but multi-tenant isolation is actually one of k8s' weak points -- for example by default you can access services in any namespace, and you need something quite specialized like Calico and/or Istio to actually isolate your workloads. Plus you're still running workloads in containers on the same node, so inter-workload protection is nowhere near as good as if you're using VMs.
I see the big value add of k8s as making infrastructure programmable in a clear declarative way, instead of the imperative scripting that Chef/Puppet use. This makes it much easier to do true devops, where the developers have more control over the infrastructure layer, and also helps to commoditize the infrastructure layer to make the ops team's job easier, if you ever have a need to run your own on-prem large-scale cluster.
There is something to be said about having the infrastructure in mind though. That's why I'm inclined to use something like Elixir/Phoenix for web-based projects. Some (not all) of the ideas that K8S brings to the table are already built into the Erlang/OTP platform.
As for Heroku, there was a recent announcement that I think shifts things quite a bit: https://blog.heroku.com/buildpacks-go-cloud-native ... having standardized container images that runs buildpacks.
The ecosystem and tooling is not quite there yet, but I can see this as significantly reducing the investment to put into Dockerizing your app for K8S.
At that point, for the hobbyist, it might be:
Prototype -> Heroku -> K8S with an Operator that can run the buildpack
K8S is really a toolset for building your own PAAS. If there were a self-driving PAAS (using Operators) targeting small hobbyists that will run cloud native buildpacks, then the barriers of entry for a hobbyist using K8S is much lower.