YouTube and others pay for clicks/views, so obviously you can maximize this by producing lots of mediocre content.
LinkedIn is a place to sell, either a service/product to companies or yourself to a future employer. Again, the incentive is to produce more content for less effort.
Even HN has the incentive of promoting people's startups.
Is it possible to create a social network (or "discussion community", if you prefer) that doesn't have any incentive except human-to-human interaction? I don't mean a place where AI is banned, I mean a place where AI is useless, so people don't bother.
The closest thing would probably be private friend groups, but that's probably already well-served by text messaging and in-person gatherings. Are there any other possibilities?