TG and sdr have a point.
However, an additional issue (it is connected but not redundant) is that those older, walkable areas tend to be located in historic centers of commerce and finance.
Detroit is also one of these.
However, unlike Manhattan or San Francisco, the financial center of that city was basically liquidated and the population pushed to the suburban and exurban periphery.

No matter how walkable Detroit is, it can’t escape its economic situation.