The first point isn’t an argument for fun but for individualism, almost to an extremist extent. If you want to publish your thoughts for others to see you’re going to have to accept the fact that some people are just going to take it differently because it human experiences are diverse, and you must be mature enough to be accountable for what you say. It’s people’s problem that they see conflict with others as an inherent negative when the disagreement with others is what itself brews creativity, because it challenges your point of view.
People criticize the media for being “biased” but then crave echo chambers of their own.
Silicon valley has a history of producing things that initially don't have a lot of restrictions that get a lot of traction that then turn all corporate and sterile as soon as big money gets involved.
Lack of fun is one reason. User generated content is risky. It needs moderation. Somebody might express themselves in ways that are inappropriate for the widest possible meaning of that word. And that might lead to legal consequences. Which adds cost. Fun and edgy things are typically bordering on inappropriate; or flat out inappropriate if you have no sense of humor. The difference is not relevant. If somebody might get offended, it's risky. Which makes the lawyers nervous.
Another reason is the obsession with building walled gardens and claiming full ownership of everything inside those walls. It leads to locked down experiences where creativity is basically not welcome unless sanctioned from the top down. Facebook, Linkedin, Twitter, etc. used to have APIs and an ecosystem of people building stuff on top of that. As they grew, all of that went away.
Facebook is a good example as something that started out to enable some wildly inappropriate and immature behavior. Mark Zuckerberg actually started out building a platform for rating girls called facemash. Controversial, even at the time and it got him in trouble. Facebook is what he did next.