An aside - I was talking about the wave of mostly white, young, single, affluent people colonizing and gentrifying Portland, not LA. The Amazon boxes are a form of gentrification that push out existing homeowners. Portland's historically Black neighborhood of Albina was a thriving mix of SFHs and medium density. Now those houses are torn down and it's a wall of condos and apartments that all look the same, each with a sushi restaurant or an organic market.
You're right, it is that there is denser zoning in close proximity that makes us want to live where we do, and makes it walkable. Which contradicts the idea that I'm making a NIMBY argument. I don't want to live in an all-SFH suburb or in a high density zone that's all rentals. I also don't want to live in the only SFH surrounded by condos. I think your point is that the SFHs don't contribute anything to the mixture, and are somehow parasitic on the higher density zones. I think that's not true. Both sides of the mix are important. It gives the neighborhood a character that doesn't exist in most American cities, which is: People of different backgrounds sit together outside cafes and talk. On any given day we hang out with other homeowners, their kids, young professionals, and also people who work in the service industry who live in the neighborhood and go to the same places they work on their days off. We go to concerts with them, they come over when we BBQ and hang out at our house.
My argument is that this arrangement is much better for society as a whole, and for individuals across the socioeconomic spectrum, than a division between all-SFH suburbia and all high-density inner city. Especially now that most people don't commute to an office, and most of the commuting is done by wage workers who have to commute out to the suburbs to work in a strip mall. The homeowners close to downtown provide an economic base for higher-end local businesses that renters would not be able to support. The people who work in those businesses earn enough to rent in the neighborhood where they work. With all high-density, families are essentially exiled to the burbs, there is little to no socializing between economic classes, and everyone has to commute.
Sure, re-zoning doesn't affect individual homeowners immediately, but the endpoint or goal of it is to ultimately get rid of SFHs in inner areas, not to leave a healthy mixture standing. That's what I see as the problem. And I think it's a politically motivated goal based on the idea that no one should really own a SFH (or if they do, as one poster put it, they can move somewhere far away from the city).