If you drive around Sorrento Valley/Mesa you’ll see that most buildings have For Lease banners across them. (Except the Q buildings, lol)
My husbands firm (architect) has done a lot of tenant fit-out work in the past, but there aren’t a lot of commercial/business spaces being modified for new tenants compared to 5-10 years ago. Most businesses are ‘sheltering in place’, downsizing, and renegotiating their leases. (His employer did that – has given up 2/3’s of their office space as the business has shrunk.)