I'm a major REST advocate (spoken at conferences, written about it in books, etc) and I've been using GraphQL for a few months now and after an initial learning curve I love the flexibility.

But in my opinion, the answer is: write code once, expose both interfaces.

Here's what I mean...

I've been writing my APIs as GraphQL first. Then putting a very light wrapper around GraphQL to expose a REST interface. The REST interface is gold standard (HATEOAS, Json-API, etc) yet it is only a few lines of code. I just have a dictionary of REST -> GraphQL mappings and transform the GraphQL result to Json-API.

Then I also expose the GraphQL interface. So users that want to use GraphQL can.

It's a win-win and it didn't take me any more time to develop than just REST. As an added bonus, the GraphQL code is inherently easier to unit test by nature.

GraphQL has a lot of flaws (for one it has nothing to do with graphs -- nearest I can tell the name is only because it was first used for Facebooks graph database) and things like pagination and error handling have no standard way to do them. But it is very flexible.