CNI is optional, you can have workloads bind ports on the host rather than use an overlay network (though CNI plugins and kube-proxy are extremely simple and reliable in my experience, they use VXLAN and iptables which are built into the kernel and that you already use in any organization who might run a cluster, or the basic building blocks of your cloud provider).

CSI is optional, you can just not use persistent storage (use the S3 API or whatever) or declare persistentvolumes that are bound to a single or group of machines (shared NFS mount or whatever).

I don't know how GP thinks you could run without the other bits though. You do need kubelet and a container runtime.

kubelet isn't, but CNI technically is (or can be abstracted to minimum, I think old network support might have been removed from kubelet nowadays)