It's a very cool system. I completely understand why people half-jokingly call it a "distributed operating system." It does a lot of things related to the lifecycles of various state (secrets, storage, config, deployments, etc).
However, I believe it goes way too far into putting infrastructure into non-cloud-managed state machines. Things that exist in most modern clouds are being reinvented in K8s. What's more, is that K8s objects are being created as interfaces to the underlying cloud objects. So you now have 2 layers of abstractions, each with their own quirks. It's too much.
Not to mention that IaC for K8s is extremely immature. This will improve, yes, for some definition of "improve." But if you've ever written Helm charts that integrate with Terraform, you'll know about all the spinning plates you have to keep balanced.
It's not a system I see sustaining into the long term future. Google may continue to use and support it forever, but afaik, they are the most invested in its success. Other cloud platforms, like AWS, seem to be focusing on not re-inventing all of their cloud offerings in K8s.