I do also love itter.sh

To me, I'd summarize the situation something like: The modern internet is one of continuous popularity contests, engagement farming, and status wars. The old internet was one of authentic sharing, rambling, and candid conversations.

But what are the causes driving those effects?

I suspect one key dividing line is the importance of feedback metrics. Likes, upvotes, downvotes, shares, whatever.

Imagine going to a party where whenever you said something, everyone briefly did a thumbs-up or thumbs-down motion to indicate how much they liked it before the conversation continued. Obviously, that's a bastardized way to party. But it's our whole world online. We compete for popularity, and we copy popular behaviors, in search of an attention-farming fixed point.

I also think the size of the community matters a lot. I remember in the earliest days of reddit, noticing the same usernames over and over made it feel like more of a community.

Modern "social media" is not really "social"; it should really be called "DIY broadcast media" in my view. A key clue here is despite our brave "social" world, the concept of an "online friend" is considerably diminished relative to what it once was. You tend to be either smothered with attention, or totally ignored. I prefer chilling out over fighting to get a scrap of interaction.

BTW here's a fun old-school guide to internet culture: https://www.flamewarriorsguide.com/ (I don't think it describes the modern internet very well)