Yes, so the cost benefit here is not in favor of GraphQL. If both technologies ultimately suffer from the same issues (what to do about unpredictable clients), but one is far more complex to implement and use (GraphQL), then there's a clear winner. Spoiler, its not GraphQL.
Page specific endpoints, I would argue, can do 99% of what GraphQL was trying to do. If you want to use it as some sort of template language for constructing page specific endpoints, that could be useful (the same way xml schema is useful for specifying complex xml documents).
But you can optimize a page specific endpoint, and do it with REST-style endpoint to boot.
Having a bunch of "simple" calls and optimizing for the "complex" ones that you need using metrics/analysis is what you should be doing, not creating a complex API that is far harder to break down into "simple" cases.