HTTP/2 doesn't fix the problem of loading data dependencies over a connection with a noticeable round trip latency. Even with server push, you need some way of defining what is to be pushed.

As a very contrived example, one page might show users who have access to servers in availability zones in aws regions. With an unnested rest api doing nothing intelligent with server push over a 250ms round trip, you're looking at a second of overhead just for sending ids back and forth.

Of course, there are ways of defining inclusion that are closer to restful than graphql is.