It's just a feedback loop optimized for "engagement" which is the metric these companies are using to make more money from the companies buying ad-space. Occam's razor and all that. It's just about money.
I think there are still lots of people that are on-boarding. And over time they simmer down. Much is poor etiquette unwittingly forced, as we have finger fumbling interfaces.
So social networks have devised a way to profit from public the discord you instigate.
HN is far more simple in approach, but you only really stand a chance if you monitor your own thread. Kind of. So you just end up glancing this and that. Or trying to read something and then give up. Threads only get traction for about a day and people fall off reading them precisely because engagement requires a silly cognitive leap.
Natural conversations are a bit all over the place, but the brain is quite good at forming some kind of narrative. Despite participants sometimes have wildly differing interpretations. These aren't even apparent in the moment. Ruminating delays, and going back to conversations from yesterday doesn't much happen, unless you have quite an intimate relationship with someone, or you are very topic focused.
Throw many disjointed feeds into the mix, and how on earth do you navigate them, let alone participate in them.
About the only thing that kind of works for me when thinking back is something like newsnet, with basic topic threading. With well considered posts.
Apologies for adding to the noise.
I have never really used Twitter until very recently. It was shocking to me how much the algorithmic content insertion drives the conversation. E.g. I click on a link to read an individual thread: right in the middle of it, with almost no visual indication Twitter is inserting completely unrelated but "high engagement" content. It's brutal.
Edit: imagine group chats sorted by engagement... a pile of responses in a disconnected sequence. Someone said something funny that got 10 likes? Push it to the top for the next 2 hours! (I am tempted to build this as an experiment just to see how awful—or effective?—this would be like.)