As these nutrient-enhanced commercial dog foods are expensive, would a home-cooked meal of hamburger or rotisserie chicken mixed with a cooked egg and sweet potato be a healthy alternative?

This is a perfectly acceptable approach that is far better than the average commercial dog food. It would be health-promoting and nutritionally sound, and varied enough to prevent most problems from developing. Especially, when people look for ways to try adding additional wholesome food sources in small amounts, perhaps reserved from meals for humans in the household, to be intermixed with the pet ration. And while that is not a scientific approach, we can tell you that calling something scientific is quite a relative term. Keep in mind that pet nutrition is based on knowledge gained from human studies to a large extent, which are flawed and inadequate to begin with. There are still many holes and blind spots in human thinking about nutrition and the same limitations will flow through to presumed veterinary oversight of animal nutrition decisions and practice. If people share the healthy dietary choices that keep them going with their pet, they could do much worse in relying on the marketplace for a well-rounded petfood that is safe and truly life-promoting and sustaining to gain the full lifespan potential.