For TV and radio there’s a finite resource (radio spectrum) which is then allocated by government permission. OTOH, it’s much easier to set up a website and pub

For TV and radio there’s a finite resource (radio spectrum) which is then allocated by government permission. OTOH, it’s much easier to set up a website and publish some content or even host conversations, than it is to set up a TV station. So the finality of the state you describe seems far from obvious — determined folks (a minority) will likely have the opportunity to opt out. It’s a different matter whether the same “ease of forking” which allows new platforms also promotes fragmentation. Maybe people learn to value community enough that some of these niche platforms coalesce to coexist & flourish. To have fruitful interactions does not require the platform to have “scale”. And over you take away scale, most of the problems afflicting these platforms also goes away; they are problems of our own making.