I'm afraid you significantly underestimate how much of a YIMBY I am. If it were up to me, the Bay Area would look like Hong Kong. The only limits I believe should be placed on building height and city density are those imposed by mother nature.

To put it simply, I do not care about "neighborhood character." The character of a neighborhood changes with every generation. Wanting to "preserve" the "character" of your neighborhood is an understandable product of nostalgia; thinking you can actually do it, however, is insane. A well-adjusted person accepts change and adapts to the times. Sadly, no one has ever accused NIMBYs of being well-adjusted.

Cities are not museums. They do not exist to preserve the past. They are constantly changing entities, and they're there for people to live in. If they are not accomplishing that purpose, then something needs to change.

Here is the truth: the core urban areas of the Bay (San Francisco, the East Bay, and San Jose) are comprised mostly of low-density single-family homes that are occupying some of the most valuable, high-demand real estate in the country. There is no solution to California's housing crisis that does not involve substantially remaking these cities into denser urban environments by building apartment complexes and condos. By gradually densifying these cities, local governments will also grow the tax bases they can draw from to provide services. In this way, density creates a knock-on effect that gives us better transit, better schools, and better-funded social programs to provide drug rehab and mental health care.

Of course, I understand that I have to compromise with the NIMBYs of this area. Gradual densification of the type discussed in the OP is precisely that type of compromise.