I should have seen it coming in 97 when I introduced an acquaintance to IRC or similar, expecting the same enlightenment I saw, and the first thing he did was start spamming channels with swears as a laugh.

Had exactly the same experience.

many of us place it a bit earlier. [0]

[0]: https://en.wikipedia.org/wiki/Eternal_September

While I agree that was the end for Usenet. And it for told what would become of the wider internet. 2005 saw the creation of the modern social network and the start of the centralized services we have today. A move from 100's of niche forums and blogs to a few social networks. Which is where I place the beginning of the end of the wider internet