What a stupid article. Usenet has been quietly doing the same thing for decades, it never fell. The real reason Google groups is being shutdown is likely their partnership with Giganews ending. GN freely peered and hosted the content for Googlr, and GN was sold a few years ago.
Seriously people nowadays seem to be utterly convinced that not having endless growth that increases every year is a failure when that's a metric mostly used by fucking shareholders, not mattering to user quality