CRs that simply instantiate an instance aren't all that useful IMO. they're much more useful if you have something like Prometheus' case where they want to attach configuration to various Kubernetes resources and can't easily fit it in annotations.

i don't know that i would actually recommend Helm for much though, since dealing with templates beyond a basic "sub string into field" use case is pain and misery. once you start dealing with named helper templates that operate at different scopes and all but the simplest control flow, the lack of tooling makes debugging templates a nightmare. the operator ecosystem has its own problems (i still can't tell what the extra Red Hat stuff beyond kubebuilder is really helping with and can't stand updating it), but having an actual programming language and all the accompanying type checking and testing tools available is a major benefit.

if you don't need something complex, kustomize feels much less breakage-prone than Helm, though its patches aren't as intuitive to write.