The trend in human nutrition is to stay away from processed foods. If it doesn’t rot it is not good for you. If you don’t recognize it as what it says it is on the label, then it is probably processed to hell and back. From my own personal experience I have been in the dog biz for 35 years. There is no doubt that when people started feeding stuff out of a bag instead of table scraps, dogs began to join the obesity parade, develop massive skin and ear infections as well as many other internal ailments that vets treat. I cynically think that vets are recommending bagged food these days because they are selling it themselves. I don’t buy my groceries at my doctor’s office why would I do it for my dog???
If you search diligently you can feed your dog real food, chicken frames, necks, offal, table scraps, etc. for a reasonable cost. I like BARF for my dogs. Last year I lost a 14 year old akita who had been on it since I adopted him, that is a ripe old age for an akita, I have a 14 year old little brown dog right now who has been on it virtually all of her life.
Now many dogs do live a long life on bagged or canned food, there is no doubt. And there is also no doubt that some people smoke their entire life and do not develop lung cancer or smoking related illnesses, but I am not taking the chance so I don’t smoke and neither do I eat processed foods or feed it to my dogs.