I dream of a SQL like engine for distributed systems where you can declaratively say "svc A uses the results of B & C where C depends on D."

Then the engine would find the best way to resolve the graph and fetch the results. You could still add your imperative logic on top of the fetched results, but you don't concern yourself with the minutiae of resilience patterns and how to traverse the dependency graph.

Isn't this a common architecture in CQRS systems?

Commands to go specific microservices with local state persisted in a small DB; queries go to a global aggregation system.

Datomic?