But my main pain points are around Kubernetes and all the hidden stuff.

Kubernetes alone is not enough, you need terraform or helm (or both) to have something manageable and deployable by a team. When things errors or do not behave the way you expected it all become so complicated or cryptic, that you sometimes better delete an entire resource than understand the underlying issue.

Some stuff like dependency between resources (e.g: Deployments depending on ConfigMap, updating the ConfigMap won't restart the deployment) makes things a lot more complicated than you expect.

There are too many vendor specific stuff that are necessary to make a Kube cluster works that you can not expect to have one terraform setup that is multi cloud. etc...