exactly my point, focus on "gated" and "small". What do you think is it that distinguishes gated communities from the generic facebook newsfeed? The right to censor, judge who gets in or not, be able to exclude bad actors, and to have stake and identity when commenting, and to set common rules for conduct. the internet is transforming from a public space to an internet of private gated communities.
In this the internet perfectly mirrors declining cities that do not maintain their commons. A lot of fractured, tribal communities emerge who are not in contact with each other, the marketplaces and houses degrade, and a huge amount of resources is spent on simply insulating oneself from everyone else. It is not a pretty picture.
On who gets to decide what taboos exist? There is no need for a moral arbiter. In communities that function well taboos and rules reflect the consensus of its constituent members. The fact that Mark Zuckerberg gets to make institutional decisions for 2 billion people is another sign of dysfunction.
"Uninhabitable?" To me it seems like the web is plenty full of people, especially in the gated communities of the social networks. Small community forums are still running as they always have. I would even say that things have improved noticeably since 2016, which was a low point.
When you say "uninhabitable", I suspect that is actually code for "uninhabitable to me." I also find certain parts of the web distateful, and I avoid them. There are other places where I spend quite a bit of time, and I don't find them uninhabitable at all, nor do I find them becoming generally worse off.
The problem with your statement about taboo enforcement is the question of which taboos do you select? There is no such thing as an impartial viewpoint here. Creating a moral arbiter with actual power is just creating another cultural battlefield that will oscillate between left-wing and right-wing control. In that, it will further entrench the current two-party duopoly and prevent meaningful change. It will also force businesses to be dragged further into the conflict, and may eventually lead to explicitly partisan companies--something I hope to never see.
Frankly I find the mores of contemporary society to be awful. I wouldn't want their taboos enforced on me. In fact, I would actively resist it using whatever measures I could muster. But since I have the option of moving to spaces where dissent and nonconformism is allowed, I choose to do so.