If you lowered the estate tax exemption to $50,000—-just enough to avoid having to value personal property—-then the step up basis rule would be fine. But at $11MM it’s a major loophole.
"sorry, I know you've spent the last 10 years living with your aging mother in her home, but now that she's passed away you'll have to sell it to pay the 40% in its value in estate taxes" -- not so attractive. :)
No one likes paying taxes. But the status quo you are advocating for is a major loophole. It allows for significant amounts of capital gains to never be taxed at all. That inappropriately favors capital over labor.