> less than they're paying now because there wouldn't be so much housing scarcity

And now we’ve circled back to where the owner of a big house looking to downside isn’t made better off.

Housing policy is complex and tied up in economics and emotions. Arguing (as you seem to be) that all users of housing are made better off by a policy change that’s so simple and obvious that no one has tried it is going to leave many people more skeptical of your idea, not less. Arguing “these users are made better off at the expense of these other users is probably more accurate and more persuasive”; if you can’t find anyone made worse off, it’s possible you’ve cracked a problem facing society for well over a century, but it’s more likely that you just have thought/looked hard enough.