Love this article. And I agree that Reddit could have been a valuable successor of the Usenet after the Usenet effectively got shut down when Google sunsetted Google Reader.
Good write-up, but I don’t agree with the premise or conclusion (“the end of the useful internet”). If valuable knowledge and communities scatter away from centralization, we might have a harder time finding them. And yes, there is/will be more public detritus. But that doesn’t mean the web isn’t useful anymore. It just requires a new (or old) approach.