Agreed that the article fails to empathize with different preferences - I would also argue that it really only considered one side of the environmental argument. Density leads to efficiency in many cases, but the culture of high consumption, travel, and general activity that is promoted by density can result in more pollution rather than less.
In the ideal if we could hold human behavior constant, high density would still be more efficient per capita. Also certainly there are suburbanites who consume and travel with the best of them - but to an individual who is self-aware of their carbon footprint, living in a less dense area may even be an improvement (for instance if it makes the idea of a walking or bicycling commute less unpleasant). And certainly our planet cannot support billions of people driving and buying new plastic toys every year in perpetuity, regardless of where or how densely they live.
Ultimately, if we want to fix the environmental/ecological issues our species faces, it will take more than building some new residences in major cities. This isn't to say it shouldn't be done - but the article definitely seems to overstate the impact of it.