There is no noise. Size of configs is close to optimum. Cross cutting concerns are easy to express. Quality of configs is very high similar to well typed code with algebra on types, this idea of values are types and lattice based unification is very intuitive.

...and we are generating manifests for "older, more production-tested systems", ie. docker compose for docker vms/swarm services - it's really great for that.

Managing configuration at scale or when the person SRE'n is not the same person who wrote, configured, and deployed the application.

Marcels latest talk has a good overview of these problems solved with CUE (https://cuetorials.com/videos)