Maybe in our plague-ridden new world order the idea of dense urban areas is just flawed. City living is great for the wealthy and indentured servitude for pretty much everyone else.
I would probably live in a trailer if they were priced cheaper than other options and not in a terrible area. The latter is usually what kills it, as most cities have zoning laws that relegate mobile home parks to areas far from any kind of development.
Another complication is that in hot areas (the dense urban areas), most of your rent is going towards location, not to recoup the cost of building the thing. I have no doubt that in SF's financial district, they can probably recoup the costs of the building in a small number of years. I wouldn't be surprised if the land they're built on is worth more than the building on top of it. It doesn't make any sense to put up a building that's 10% cheaper, but ugly, when it only makes the whole project 0.1% cheaper.
That's the problem with most of the cheap/tiny/etc. housing schemes. By the time you account for whatever combination of land cost, overhead of common areas/access, utility infrastructure, maintenance, etc., you now have housing that is often substandard in some way that isn't actually much cheaper (and is going to be harder to rent/sell/re-sell).
But I could see modular designs helping theoretically.
Unless the architect designs around the predictable weathering patterns, a brutalist building really needs constant upkeep to keep looking good, just like some other contemporary styles.