My understanding of the advantage of GraphQL is that it allows you to load a structure like

    user {
      groups(first: 10) {
        posts(first 1) {
          content
          author {
            name
            address {
              state
            }
          }
        }
      }
    }

and have all the round-trips take place within a datacentre, instead of needing to query

    /user 
    /user/12/groups?limit=10
    /groups/34/posts?limit=1
    /posts/56
    /users/78
    /users/78/address

and without having to write a separate

    /top_posts_view

endpoint.

I don't understand from the description "a thoughtfully designed REST API built according to HATEOAS" what your proposal to solve this problem is.