But even without them, it makes little sense to have a potentially functioning, commercially viable plot of land sitting empty.
“It makes little sense” and yet it happens all of the time precisely because unlike the fictional policy set you concocted for your argument, we actually don’t incentivize people to make the best use of their land through property taxes.
Most localities in the US tax land improvements instead of the land itself, which is the exact opposite of what you were saying we do.