People were saying the exact same things two years ago.
Note that it may actually be true. One way to look at it is all successful organizations and communities are continually dying. In order for an organization to get critical mass and start attracting people, it has to be far above the mean in quality; the mean idea, after all, never gets realized. After that, everything is regression to the mean, i.e. downwards, until it ceases to exist.
If you rarely discover real places you've never been to, the memory will just be compressed and it seems like last year that you moved from your last place, when it was actually forty years ago.
Now, this can be alleviated by instead of visiting new places learning new things, but those things have to be actually new to your brain and not just more of something you are already familiar with. Otherwise it gets compressed all the same.
Subjectively it felt like I lived about 5 years in the first 2 months after my first kid was born - certainly they were more memorable than the previous 5 years. We were basically confined to the apartment except for doctor's visits during that time period, but the experience of caring for a little person was dramatically different from everything that came before. And then the newborn periods of our 2nd and 3rd kids flew by, because we had all the routines down.
2020 also felt like I lived a lifetime in a year, even though we were shut-in, because of all the events and changes of routine that year.
When I was a kid in the 1960s, World War 2 was ancient history, but at the time, it was only 20 years ago. And now, 20 years ago is only yesterday.
Then their children show up and the cycle repeats again.
Time flows like a river, and history repeats itself...
See several thousand year old commentary on how the youth is rotten
Eventually you end up with stackexchange or Reddit or 4chan where 95%+ of posts are bots or at least LLM generated, and the remaining 5% is crazy people who refuse to leave. HN is behind in that cycle but will inevitably and unavoidably catch up because as I stated there's no repair mechanism. All successful online orgs and communities attract bots and LLMs that kill the organization. There is no immune system other than unplugging and touching grass IRL.
My guess about "large scale socioeconomic effects" is we can't talk about Dead Internet Theory in public in polite company, but we can talk about "too much LLMs" or whatever in a vague sense while describing all the symptoms of Dead Internet Theory. Like those people who complain about poop on the sidewalks but can't be permitted socially to declare any sort of dislike of homeless people, so the talk is focused solely on the symptoms as if the symptoms appeared magically, an uncaused causation. The advertising fraud bubble will pop, eventually, and it'll all be blamed on LLM bots on social media, it totally wasn't planned and aided and abetted by the companies themselves, no, LOL. Their profits off advertising fraud were totally accidental and unintentional, you see, so they should get away with it. The people to blame are those vague AI bot things that magically appeared and totally had no legally prosecutable humans behind them.
Another large scale effect to talk about is massively pulled forward demand. A decade or two of Facebook and that pulls a lifetime of demand forward. What happens when the bill's due and nobody left but a tiny fraction of hopeless addicts? If the population as a whole does a lifetime of doomscrolling in 20 years, the next generation at least will be a total drought. Internet access will never go away because its too useful to pay your bills online, but social media will almost certainly go the way of the late 1970s CB Radio crash. I assure you CB radios are still being made, people still making money off them, and people are still using them, however only a microscopic fraction of the population uses CB Radios. So it will be soon, for "socializing online".
When you have a mirror, you can shine light wherever you want.