I think a lot that has to do with limited parking available with most mixed-use development.
If UTC mall was in Asia, you would build a 50 story apartment/condo building right on top of the mall within 100′ of the trolley stop.
I’m guessing in SD, mixed-use would only work in existing retail locations that retained the same mix of stores that currently exist and same amount of parking.

We’ll get to see how this experiment will play out with the new housing zoning by the City Council.
27k units in Kearny Mesa
25k units in Mission Valley
6k units in Midway
10k units at the Navy/Old Town facility
28k units Mira Mesa