I think you and the OP might be making the same point - that if policy dictates that tax breaks on mortgage interest deduction are capped at 750K then why is it acceptable to give members of professional sports oligopolies tax breaks for hundreds of millions of dollars?

I’m not a disagreeing with the idea that tax breaks for stadiums is a bad idea. I’m saying something like mortgage deductions are evidence of the same type of bad policy for many of the same reasons. The OP seems to indicate one is bad while the other is good.

There are very few cases where mortgage interest deductions are better than the standard deduction.

That's only because the state and local tax deduction was limited at the same time as the mortgage interest deduction was (further) limited. The standard deduction also increased.

Prior to that, it wasn't uncommon for people in higher income tax states to exceed the standard deduction with SALT and mortgage interest.

> It tends to incentivize the wrong behavior (excessive housing size/mortgages and being a regressive tax that favors the wealthier propertied classes).

In Canada mortgage interest is not tax deductible. What's done here is that, for your primary residence, any rise in value (capital gains) is not taxed when you sell it.

The US and Canada have roughly the same home ownership rates.

The mortgage interest deduction was one of the few things enabling upward mobility for middle class citizens. Too many policies are governed based on one perspective. There was a cap on the profitability that could be garnered on applying it, but that was driven even lower in the past 4 years to make it almost worthless now.

The ability to save money and to be able to work your way out of economic instability is not a favor that government grants people. Upward economic mobility is one of the few things that held the social contract of taxation in place. Without upward financial mobility rules, taxation is simply a forced and pretty pohony "mob protection" fee.

>few things enabling upward mobility for middle class citizens

The opposite is true. It inflates home prices (because it incentivizes larger mortgages) which ends up pricing out people from the housing market. It can also lead to increased defaults.

It doesn’t provide upward mobility. It’s simply a politically popular way to favor a specific class of voters.