The problem with McMansions is usually too much house on too little land, with no visual relationship with neighboring houses. On a bigger lot with more trees and space around the house, most of them wouldn't look bad.
The primary mass is formed by the central column and the two main wings that stick out to the sides (primary mass should be evaluated as an artist would, not by simplistically the largest box of the house). It has asymmetry, but it's cohesive, not awkward, asymmetry, and it's definitely balanced. The proportions make sense in the context of the terrain, because the widest portion is drawn along the edge of the hill, melding with the ground, and the bottom portion is filling the gap in the valley. It definitely has rhythm, because all of the balconies and windows are drawn from the same palette, cohesive again.
1: http://architectural-models.com/newsite/galfallwat.html
Edit: I just noticed that model is $61,000!
Classical mansion typically has more details and larger number of different visual elements than Fallingwater. Mansions make them fit by using the rules mentioned in the article. Fallingwater uses smaller number of plain elements to create organic arrangement.
On the other hand, the problem with Fallingwater is that it leaked, was full of mold and mildew, and was structurally unsound. It failed at the most essential functions of a house: standing up and keeping the rain out.
If you want to be a sculptor, you should be a sculptor. If you want to be an architect, you need to design stuff that keeps the rain out, the heat in or out (depending on climate and season) and the noise and odors of the neighbors away. Yes, Frank Gehry, I'm looking in your direction, as well as that of FLW.
Then we had every architecture student and their dog doing something bit similar. Some of that stuff got pass because of Fallingwater is nice. But most are hideous.
Once you know the rules, you know how to break them Personally, I dodge the bullet by simply going for Bauhaus. Farnsworth > McMansion.
Modernist and postmodernist architecture isn't trying to imitate classical mansion architecture.
> Disclaimer: These same principles do not always apply to Modernist or even canonically Postmodern architecture. These principles are for the classical or traditional architecture most residential homes are modeled after.
Those bungalows were definitely not modeled after classical or traditional architecture, so the principles in the article wouldn't apply. I'm sure the author has different opinions about modern architecture (i.e. the style that FLW defined).
The difference is that McMansions are (poorly) aping traditional architecture, whereas FLW was creating his own style.
For example, all the windows are similar, the house appears designed in thirds, the bottom floor clearly visually supports the top floor.
The house is an example of what the article calls an "assymetrically balanced house." Wright was even kind enough to point out the balance point with that flower-podium feature.