We have had some big builds go up. I know many tenants have reduced their own foot print too.I think CBDs will always exist, but they'll change and the percentage of employees physically attending CBD offices will naturally continue to dwindle over the coming decades. I think we'll see (say) the same office building with 1,000 desks rented by ten employers of 100 desks each rather than five with 200 desks each.
CBD rents will naturally decline with market forces and fewer office buildings will be built, in favour of apartments since I think there will always be a market for singles, couples and students for city living.
Here in Adelaide, 60 King William Street has just finished construction - it was conceived before the pandemic. It's the largest office building in Adelaide by lettable floor area, but its anchor tenants will be Centrelink, Child Support and Medicare, government agencies rather than the private sector. A few hundred metres away, the almost-complete Festival Plaza tower's anchor tenant will be Flinders University.
I agree though, focus needs to go to getting the CBD population up. I know it's a challenge to refurbishment old office buildings to residential use, but it's not impossible and there are plenty of examples around the world.