actual autocracies that crack down on this kind of speech

The ball is rolling. Action against media organizations is already underway. You already couldn't publish this message via CBS, WSJ or the Post, for example. They likely wouldn't even interview the author.

But yeah, it takes time, censorship is hard in practice, and random substacks are fairly far down the list.

But pretending that this is a "healthy" democracy at this point is pretty strained reasoning.