I think "bare" Kubernetes is still a quite nice tool that allows for learning transferable skills across clouds (similar to Terraform). E.g. even if I have to spin up my own nginx-ingress to be able to handle ingress resources, after having learned that initially, I can basically do the same thing across clouds.

It's just that GKE (Autopilot) does a lot of those out of the box for you that, so you get a much easier end-to-end experience for non-admins (= "request resources -> have them instantiated").