While storage generally not a simple problem, Kubernetes' design makes it even harder. Why Kubernetes went this way is not entirely clear to me. One of the reasons could be its owners' focus on cloud infrastructures and tutorial-level developer use cases, where you want to show how to dynamically create and consume a file system backed by GCE persistent disks or EBS. Also getting a secure and usable Kubernetes setup running is currently a lucrative business model.

But as the OP writes, the standard case it should support is secure access to existing storage, and Kubernetes fails there on all levels. Simple things should be simple, hard things should be possible.

In its API design, it hides storage under abstractions like PVC, PV, StorageClass that most users have not seen before in their career (where do they come from btw?) and which do not re-use general system architecture concepts. Worse, these abstractions do not have exact definitions as their semantics can be massaged with access control rules.

Consider the most simple case: mounting an existing file systems and authenticate with a Kubernetes secret. You should be able to do this in 3-4 lines in a pod defnition. Instead you need to create several yaml files, whose content is strongly dependent on how your Kubernetes was set up, so no general tutorial will help you (but others are, see above).

And this is just for getting the basics going. Secure access / user authentication is still unsolved after two years (https://www.quobyte.com/blog/2017/03/17/the-state-of-secure-...), and does not seem to be high on the agenda neither in Kubernetes nor CSI.

There are other basics missing (like file systems do not have necessarily a "size"), but let's not go into detail there.