The whole premise of opengitops is heavily reliant on kubernetes.
There's indeed a fair degree of short-sightedness in some GitOps proponents, who conflate their own personal implementation with the one true GitOps.
Back in the real world, the bulk of cloud infrastructure covers resources that go well beyond applying changes to pre-baked Kubernetes cluster. Any service running on the likes of AWS/Google Cloud/Azure/etc require configuring plenty of cloud resources with whatever IaC platform they use, and Kubernetes operators neither cover those nor are a reasonable approach to the problem domain.
I mean Crossplane is a pretty popular k8s operator that does exactly that, create cloud infrastructure from K8s objects.
If your only tool is a hammer then every problem looks like a nail. It's absurd how anyone would think it's a good idea to implement their IaC infrastructure, the one think you want and need to be bootstrapable, to require a full blown K8s cluster already up-and-running with custom operators perfectly configured and working flawlessly. Madness.
You can have a small bit of terraform for crossplane then crossplane for the 99% of the other resources