A recent Ash Wednesday poem starts with the imposition of ashes and then mentions a McMansion in this line:

That burned down the McMansion of my hubris

I would guess this references one of the traits of McMansions: their size. A super-sized house is analogous to the level of pride humans can construct. Their pride puffs them up in their own eyes. They impress themselves, just as a McMansion through its size and dubious architecture, tries to do in impressing neighbors and people passing by.

But the idea of the poem then is that the McMansion of hubris is demolished by the ash-delivered reminder that “Remember that you are dust, and to dust you shall return.” Large amounts of pride and large McMansions too will be brought low. McMansions might live on longer than many humans but they too will not last forever.