Are Commercial dog foods(canned and dry) responsible for the rapid deterioration of dog health since the 70's?

i have heard dry dog foods are better for the dog's health ,compared to the canned variety's? tin dog foods and cat foods especially contain far too much sugar in them,Dog books and top breeders books will recommend certain brand name foods as the best nutritional option for your pet,but a lot of this is down to company sponsership and a hefty size cheque for the author of these books!