If Midjourney applies this to all their artwork then maybe it alleviates some of the ethical concerns (Midjourney then has a "style" independent of the training data)
Therefore the only way to make housing affordable for everyone in the long run is to guarantee housing. That means social housing or rent-geared-to-income housing in combination with cooperative housing and market housing.
No one solution will fix the problem. For example for the mental health problem if you give an apartment to someone really far gone they will just destroy the apartment and walk outside to live on the street. You need supports for them maybe communal living. So the right type of housing matters for each person. For someone who will never make enough money, the housing has to be free.
Cities provide concentration of services that people need. No city, no services. They also provide concentration of jobs, and concentration of people. For an extreme example you can't have the full set of services for 1 person in the middle of nowhere without an impossible cost.
So it all depends how independent you are from everything and everyone. If you have complex medical needs or need to be around certain people also in the city, you might have to live in the city.
Homeless and mentally ill get treated by programs and services that can be afforded by major cities (small towns apocryphally throw homeless on a bus to the big city to fix their homeless problems).
If Midjourney applies this to all their artwork then maybe it alleviates some of the ethical concerns (Midjourney then has a "style" independent of the training data)