I’ve lived in Los Angeles for over 20 years, so I think I have seen what construction is like in California. And I have family in other states who work construction, so I also have an idea of how much stricter the building codes are here in CA (including how much stricter the building inspectors are). Almost everything you complained about is about workmanship or level of finish, not actual build quality. It might not be very sound proof, but it almost definitely won’t fall apart under normal use (there’s a reason that condo in Miami was such huge news). Also, if you are able to fall through a wall with 16" on-center studs and 1/2" drywall then you must be way more dense than I am, since I would have to run fast to get enough speed hitting shoulder first to break through, let alone a slow speed fall into a vertical surface. I’ve never been to China, so I can only repeat what I’ve heard that the quality is much lower than in the US.
As far as you rent vs buy example, you took the extreme case of Silicon Valley. Even in Los Angeles you can buy a single family home for $1.2M that rents for $6k/mo. You don’t even have to look at Detroit. Your example is also off. A 2b 1b apartment rents for $3700, but a condo of that size is $600k not $1.2M. And the mortgage on $600k is roughly $3200/mo plus $600/mo in taxes. If you look at single family homes, yes you are starting at $1.2M, but those are minimum 3br (or very large 2br) and absolutely not renting for $3700/mo. If you go away from the extreme case of SV and somewhere completely normal like the nice suburbs of Indianapolis, you can buy a small house for $300k that rents for $2000/mo.
https://www.redfin.com/CA/San-Jose/1995-Sumatra-Ave-95122/home/1729649
https://www.rent.com/california/san-jose-houses/3-bedroom_2-bathroom?property-type=houses&bbox=-121.8580,37.3009,-121.8151,37.3520
I can link things too. The house you linked was last sold 40 years ago for $126k, so the person who owns it is renting it out for many times more than their mortgage. You might not be able to rent out a place for more than a mortgage today in that specific city, but if you own it for 5 years then you might be able to. Also, 2br 1ba single family houses in San Jose are fucking weird. If you start looking at 3br 2ba houses in that area then it gets a little more normal. If you look at 2br 1ba condos, the prices are also more normal. But you ignored what I said about Silicon Valley being an extreme case.
90% of the country you can buy for less than renting. You asked why anyone would rent when buying is cheaper. And the answer is because buying is hard. You need to have a lot of money saved up, which most renters can’t do. You need to be able to pay for repairs, which most renters can’t do. You need to know you aren’t moving jobs any time soon, which a lot of people don’t know. And nowadays you are bidding against corporations and investors who are bidding full cash, and sellers would prefer to do that instead of waiting on a mortgage approval that might fall through.