One thing I haven't seen mentioned in comment. Dunno if Kustomize has something here. But: Helm is a shit but at least some kind of composition tool. Some way to have resource of various types associated to some top level idea.

Very very little else seems to bring this basic sense to Kubernetes. Metacontroller kind of could do that. Crossplane's whole business is this, but it's been infra-specialized: but the Crossplane v2.0 release is trying to be much more generally useful. https://docs.crossplane.io/v2.0-preview/whats-new/ . Would love other examples of what does composition in Kube.