I'm not sure this is right.
There would be an incentive to purchase unused or underused land -- the price will be lower! Relatively high taxes will encourage the landowner to sell the underperforming property rather than hold onto it for years waiting for its value to increase (speculation).
There would also be an incentive to build -- the developer can build as extravagantly as he wishes without dramatically increasing taxes. Want to build a giant tower? Tax is almost the same as if you built a parking lot.