Efficient in terms of wire transfer sure, but GraphQL tends to wind up generating queries that are quite difficult to optimize at the DB layer, so you wind up spending way more computer and time than you would otherwise need. If you're in an organization where folks with no database knowledge are writing the GraphQL queries, this winds up being a never-ending game of whack-a-mole. For anything performance sensitive, I'd much rather have a nice, optimized endpoint that returns more data than the client needs rather than have the client be able to issue any query they want.