The point that is being made, though, is that those things that do have value that exist in his writing, did not originate from him and are available elsewhere to the point of ubiquity. If you only heard about them from him, you should read more.
Why does it matter if it’s “available” elsewhere? Do you complain when a restaurant provides food that is available elsewhere?
I do my best, when I see an intellectual huckster, to point at it and call it what it is.
Those who are taken in by hucksters have a tendency to dig in about it, and that’s not my business.