I think your point is a fair one. The distinction is that it's easy to write a contextual SQL query for any one GraphQL query when your database model closely matches your API objects. "Contextual" means that sometimes this requires a "side effect" to happen (eg. creating an index on a column in the SQL DB).

Making it generic and performant at the same time is where the complexity is.

It would be akin to saying how, since knowing that you might need an index in the SQL database is simple, a RDBMS could decide to create those indexes for you.