To me, "McX" evokes the image of fast food. Something bland, unappealing, and one-size-fits-all that sacrifices quality for mass production. The later McMansio

To me, "McX" evokes the image of fast food. Something bland, unappealing, and one-size-fits-all that sacrifices quality for mass production. The later McMansions may have evolved as a response to the perception of them being generic by slapping on superficial and poorly designed accents. It doesn't change the low quality. Burger King isn't considered any better than McDonalds just because you can "have it your way". But mostly it's about the houses being unnecessarily large. Now that I think about it, the McDonalds metaphor here is probably meant to be that they're Super-Sized houses.