There's nothing that you can do with a RESTful api that can't be done with GraphQL. If you wanted to you could build a RESTful GraphQL api -- we did this at my previous company.

GraphQL allows you to do things though like query for nested data structures without making round trips, require typed arguments for queries, and pass arguments to specific fields, things that would take a bit of doing with a non-GraphQL api.

It's certainly not perfect, for example I at least have found query tuning for large nested queries to be a bit more complicated than I'd like it to be, but overall I've had a really positive experience with it and unless I have a good reason not to will be using it for any apis I'm building going forward.