The handful of dogs I knew that broke 18+ years were mutts on garbage kibble like Ol' Roy. And these were medium-sized dogs (30-50lbs), not Chihuahuas.

Anyone I know who can afford to feed their dogs raw also generally get purebred or "designer breed" dogs, and they've all lead shorter lives with more diseases (cancers, autoimmune disorders, bone problems, etc).

My anecdotal experience leads me to believe that breeding practices are a bigger part of the problem, but these are quite small sample sizes.