The top concern about McMansions is their size. Yet, a house that is big is not necessarily a problem. See this recent example of resilient housing from New Urbanist architect Andres Duany:

He then scrolled through building prototypes, developed in partnership with architect Korkut Onaran. For affluent families, Duany proposed a multigenerational alternative to McMansions, resembling the walled courtyard houses found in Latin America, Europe and Asia. These compounds’ walls protect against wind, rain and storm surge. Clusters of eight or so walled compounds would surround a central green that could be used for vegetable farms, exercise facilities or a small schoolhouse. Resilient adaptations such as backup generators, solar panels and water purification facilities would come standard. The goal, Duany said, was to design communities that could be “partially self-sufficient” in the weeks after a disaster.
Here, the large home has several advantages compared to McMansions. First, it is designed by architects. McMansions are often said to be mass-produced by builders who want to maximize profits, not aesthetics (outside of an impressive – though often jumbled – facade). Second, the home can hold a multigenerational household. If a larger family inhabits the larger home, it is not just an empty McMansion that impresses people passing by; the space might actually be used. Third, the large home is part of a community intended to stand strong in the face of the effects of climate change. McMansions are criticized for their poor building construction – possibly limiting their ability to stand up to storms and other issues – and are often in sprawling areas.
An argument could be made that large houses in general should not be promoted. Even if you have the resources, who needs a home larger than 4,000 square feet, let alone the mega mansions of the truly wealthy? For example, the Not So Big House suggests smaller but customized homes would work better for residents. Tiny houses explicitly reject the bigger is better logic.
But, if bigger houses are still going to be built – perhaps some will say they need them for entertaining or large families or for particular uses that take up a lot of room – they could be done in a way that makes them less like McMansions and more like large versions of well-designed, built to last homes. Indeed, McMansions receive a lot of negative attention even as there are plenty of supersized homes – true mansions – that might also be worth rethinking.