Kubernetes is one conceivable incarnation, but it operates differently than other infra-as-code tools. Terraform, for example, builds a dependency graph of your resources and initializes them in order. Kubernetes doesn't care about dependencies, and it just keeps trying to create resources and things will fail until their dependencies come online.

Further, Kubernetes manifests are the verbose "assembly language" layer, so you still need something for humans that is DRYer.

We use Terraform to manage Kubernetes resources (as well as cloud provider resources) at the moment, but I think you can equally use cloud provider operators for Kubernetes and manage everything with Kubernetes--I haven't tried this yet so I can't comment. In the latter case, you would still need something to DRY up your Kubernetes manifests. Also, if you aren't running on Kubernetes and you just want infra-as-code, k8s is an expensive solution (in terms of operations).

What I was picturing was a more conventional infra-as-code diffing engine (like Terraform's) but with a more verbose interface similar to Kubernetes YAML.

> Kubernetes manifests are the verbose "assembly language" layer, so you still need something for humans that is DRYer.

It's a little more than that. Out-of-the-box manifests for primitives are certainly assembly-like, you're right--but CRDs allow you to operate at a higher level of abstraction while staying in the same syntax, which is powerful and unique to k8s (everything else, from Helm to Terraform to Ansible, distinguishes between pseudo-assembly "language that directly expresses changes to be made" and "language that humans can write abstractions in").