Starting with an expressive declarative schema and building everything around it is exactly the approach we take in EdgeDB [1]. One of the key ideas is that you should be able to define almost anything not just statically, but as a result of some computation. Think views, functions, and computed columns, but without the traditional limitations and change-rigidity of their implementation in Postgres, because schema migrations are treated as a single logical change unit [2] rather than a bunch of independent DDL statements, so dependencies between schema objects and their changes are understood. The richness of the schema coupled with thorough introspection [3] then enables GraphQL schema derivation [4] and type-safe client generation without any loss in fidelity.

(disclaimer: I work on EdgeDB)

[1] https://www.edgedb.com/ [2] https://www.edgedb.com/docs/guides/migrations/index [3] https://www.edgedb.com/docs/guides/introspection/index [4] https://www.edgedb.com/docs/graphql/graphql