Department of Huh?: Skidelsky on Economic Possibilities for Our Grandchildren

I have always been a big fan of Economic Possibilities. It is a powerful essay. It makes lots of good points. It's very optimistic. And even among Keynes's enormous pile of well-written essays this one, I think, is particularly well written.

But the one area where Economic Possibilities falls flat is that it fails at predicting the far future!

Why is Skidelsky celebrating the one obvious and universally agreed upon failure of the essay?