One of those things is not like the others.
This HN website, phpBB forums, etc., don't interface with other systems. Mastodon does. Usenet and BBS' problem was more that they just predated the massive influx of always-online users that came with the advent of smartphones.
It's not like Twitter is a single server through which all content gets pushed. It's a replicated, distributed network of servers. ActivityPub servers are too, except the shards in network are not all owned by the same entity.
How would you learn about something via Twitter, sans promoted tweets? You'd find out about it from the retweets of the people you follow. That's literally the same thing you'd do in a Mastodon instance.
The big difference is that nobody in the ActivityPub network has the power to force content into your feed. Hasn't that been one of the biggest complaints of mid-2000s era social media? That the algorithm takes presidence over your own preferences? Never in my life do I want to see another "here's one weird trick you can do with a couple of pennies in the bottom of a plastic bag" click-bait article. That's basically impossible to propagate within the ActivityPub network. But that doesn't mean nothing can propogate through the network.
I'm having long, engaging conversations about topics I care about with people within the ActivityPub network. Almost none of those people are on the Mastodon instance I am currently inhabiting. I'm having more of these conversation than I had on Twitter, where I have 15x the number followers. From my perspective, my word is getting out further through ActivityPub than it ever did on Twitter.
