In reply to mark k..

@OriginalEXE,

I personally don't care "they" write something from scratch or not. I doubt most users do. What I want to know is what is the advantage to me, as a WordPress user or admin, in having something built this way. Or, to put this another way, what is so wonderful about this that I ought to ask a developer to do this for me?

At the moment, all I'm seeing is what could have been done before without the REST API. And yet no-one was apparently doing it. That doesn't make it sound like something that's worthwhile.

And, like Rick, I tested this site without JS activated, and found it loaded much faster and provided a much more pleasurable experience.

So, again, what's the advantage to users and admins of doing this?