Dogs and cats are carnivores. You only need to look at their teeth, and have a cursory study of wild dog and cat feeding habits, to understand that. Their guts are not designed to eat vegetables, and kibble is a processed food that contains bulking ingredients such as rice and potato, food that dogs can’t tolerate either.
Cats are even more extreme; they are ‘obligate carnivores’ - the nutrients in vegetable matter are not bio-available to them. They literally NEED a balanced diet of meat to survive. Dogs, who are facultative carnivores, can "survive" on a plant-based diet, but they certainly don't thrive.
Dogs’ and cats’ life expectancy has reduced dramatically since kibble was introduced as a mainstream diet in the 1950's. Many dogs suffer with long term illnesses, which can often be directly linked to poor diet, and ultimately cancer rates have soared amongst our pets (in the USA, 47% of dogs die of cancer, attributable directly to the highly processed dog foods that are widely available there).
Feeding a balanced "species appropriate diet" to our pets give them the best chance of a long and healthy life.