It's an important point that Graph makes it easier for the user not the server. You still have to do the work, which is sometimes harder because you need to take care of edge cases and performance pot holes (in case you miss something that lets your code to run away with a heavy query).

The only difference between REST and GraphQL from the server side is the interface. The underlying work is the same.

"But we can connect multiple datasources into one query!" - REST does not stop you, it's done all the time. What is the challenge, exactly?

"But we can specify only the fields that we want" - yeah, it's called URL arguments. Many services already do that with their REST API's, it's just less enjoyable to use.

Stop treating GraphQL as some revolutionary tech. It does not make something possible that was not possible before. You could still create web pages that looked great before CSS was a thing.