Even if users don’t have 5G, why is your rest api so slow that it’s an issue? Why is graphql the solution? The featured article points out that optimising rest can be a better solution, in terms of time and effort, than implementing graphql. The problem that graphql solves isn’t this one.
While I agree with your beginning sentence, the one I quoted doesn't sit well with me. It would be good to remember that not everybody has 100 Mbits fiber or 5G download speed.
We all saw the data on how milliseconds affect user retention then proceed to completely forget about it once building our apps.
I think we can do better.