If you want to disincentivize landlords through tax, it'll be through income tax to directly reduce their profit. Take away the tax deduction for mortgage interest. Take away depreciation. It's easy for most landlords to book taxable losses every year while generating positive cash flow.

Rent is always more than mortgage+insurance+taxes on equivalent property. The landlord has all the same expenses (and more) as a homeowner, passes them on to tenants, then adds expected vacancy and his profit on top.