Besides, who's to say that these desirable places are not desirable because they are low-density? It's a chicken and egg problem.
If this were true, you wouldn't need zoning, and people would just build low density because that's what everyone wants anyways.
If we're concerned about property rights, why can't the property owners build at a higher density? Or sell to a developer that will build at a higher density? The fact is the zoning at play _restricts_ property rights it doesn't protect them.
Anyway zoning was never static (it wasn't ordained by God after all), so changing it isn't really a big deal. People are angry and surprised of course, but the writing has been on the wall for a long time.
I like the Strong Towns notion of "no massive changes anywhere, but lots of smaller changes everywhere", although in practice it's not always quite so smooth.
Being part of a democracy does not mean you get to control every single action that could impact you.
Personally, I would say that lots of low-density communities do remain low-density. And generally, that's because people don't want to move to them.
But if you're a small town in Northern California, one of the most desirable places in the world, saying "we want to remain low density" is basically saying "we got here first, so it's ours -- nobody else gets to have this!"
And I think that's a fundamentally wrong way for us to organize our places. Desirable communities shouldn't be able to keep out people who want to come in, just because they want to stay exclusive.
But I don't think that's a settled point, and there is a lot of nuance to basically every adjective I just used.