How about if, at the beginning of every financial year, landlords who wanted to take advantage of negative gearing agreed not to raise their rent in the next 12-month period? And if they didn’t sign up for that, then “market forces” would determine their rents (provided they took Airbnb out of the equation).
In a market with many buyers and sellers, “market forces” determine the price all the time. Politicians seeking your vote may tell you otherwise. But measures designed to prefer one class of constituent to another usually backfire over time.