From my grandparent to me, there has always been German Shepherds in our family. Starting the 80's all of our dogs started dying much earlier, ~6-7 of cancer. In the early 2000's, we switched to raw diet from premium store bought kibble to raw. Sure enough, not only did their coat improve not a single cancer death under age of 13. I know it's anecdotal, but in my dog world circle and family, we've all observed simila…
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.