This is 100% nostalgia writing.

Yes the internet has changed, as it always has. The internet is many layers built upon each other. Under no circumstances would I consider the 2000s to be the "old internet", there are probably plenty of people in this thread who get a chuckle out of that. I assure you, there are plenty who look down on what you think was the "golden age". The procession of generations is to lament the younger and affirm Hesiod's ages of man in their own way. I'm sure you don't have to dig very hard to find computer scientists lamenting the new generation of undergrads in the 1980s who spent too much time with the low-brow, crude and totally soulless Usenet phenomenon.

The "old internet" isn't dead, and this is somewhat acknowledged by the author with a disclaimer. In fact, they make note the number of people producing work that they would normally value is higher than ever. But they lament it with a vague feeling that it's simply "not the same", not feeling like it "came from some place". That's very telling, because that's exactly a sensation of disenchantment. As we age, there are less surprises, less things feel new, less mysteries to wonder about. Patterns that were hidden and novel come into stark relief. The more pessimistically minded begin to suffer from world-weariness. Anomie sets in, and rationalization begins, attempting to ground the loss of youthful whimsy with some external phenomenon.

I would say embrace it, you were always on your way to become a crotchety old coot. That's a very important social role to play. Just don't mistake your rationalization of feelings for something substantial, it's nothing but a hard-wired delusion to help guide your development as a human being.