> IIUC any landlord can use depreciation to lower their tax bill.

This is also not really how depreciation works for assets that retain their value. If you buy a building to rent it out, the cost of the building essentially a cost of doing business, i.e. a tax deduction. You pay tax on the profit which is revenue (rents) minus costs (building, interest, maintenance, advertising, etc.) Depreciation is the building, they make you take it over time instead of all at once when you buy it.

But the depreciation lowers the book value of the building, which is your tax basis when you sell it. If you buy a building for a million dollars, depreciate it down to $500,000 and then sell it for $2M, you have a $1.5M capital gain from the sale. You basically have to give back all the depreciation unless the building actually lost that much value by the time you sold it, and in practice it usually goes up instead of down.

It's really the homeowners who have the advantage here because there is a large capital gains tax exemption from the sale of your primary residence, and that's actually a reduction in taxes instead of just a deferral.