Imagine the amount of plumbing you would have to redo for the toilets. There all sorts of codes for apartments, there must be so many windows, you need natural light in bedrooms etc
If these unused offices could be better as apartments, i don't see a decline in how cities being a great place to be.
I co-own a small city office and we've always assumed redeveloping as three-storeys with residential above commercial would be our long-term plan. It's a short walk to dozens of restaurants/cafes/pubs, short walk to a chemist, small supermarket, florist, and so on. Two blocks from large parks and running/cycle tracks, etc.
Also, there are plenty of people who work in the city who cannot work from home because their jobs require them to physically be present.
Agree that cities offer more than just a place for business to happen.