Carnivore = meat eater = Sharks, Lions, T-Rex
Carnivore = member of Order Carnivora = Lions, Bears, Wolves, etc
I will be using the second definition
The earliest carnivores were quite adept at eating all sorts of stuff: fruits, certain fiberous and tuberous parts of plants, flowers, insects, reptiles, fish, eggs, bone, muscle and organ tissue. However the bone, muscle, and organ tissue made up a very small percentage of their diet.
Think of what a modern day raccoon would eat.
What made a carnivore go on the path to bringing us giant meat eating beasts is a set of teeth called the Carnassials which were specialized in cutting meat. (Well, that and some lumps in the skull that are associated with the very keen senses that the carnivores have)
Some carnivores either kept this omnivorous diet or rediscovered it. Some went so far as to 'rediscover' herbivorous diet (Giant Panda)
The Cat family is an example of one that has gone on to become a 'supercarnivore' in that it eats meat meat and meat. One way this is revealed is to look at a cat's Teeth. It has small teeth in the front for chopping off bits, big canines for holding the prey, and then the carnassials for cutting the meat that is in it's mouth into swallow-able sizes. It also has big stretches where there are no teeth.
Now, look at a canine skull
It has a lot more teeth, because canines are still amendable to eating all sorts of stuff in addition to meat.
Of the common canines, the fox is the one that eats the most non-meat. It is an omnivore year round. The Coyote on a year round basis eats a lot more meat but during certain seasons of the spring and fall it eats more plants than anything else. Wolves are the most inclined to eat meat and only meat, but all wolves will occasionally eat fruts and nuts when extremely plentiful, and the frequency of this is heavily dependent on the sub-species. The sub-species most likely to have been the one which dogs descended from (The Indian Wolf or Arabic Wolf) take more advantage of non-meat than most other sub-species.
This is all stacking up in favor AGAINST a 100% raw meat diet.
Recently there have been some studies about the genetic divergence between wolves and dogs. What came to light is that what dogs have that wolves don't is genes that increase the dog's ability to eat starchy food.
This is being viewed in one of two ways. The first is that garbage eating wolves developed this trait in the earliest days of proto-domestication. The second is that dogs were domesticated BEFORE this trait, when humans were hunter-gatherer, and when Humans discovered agriculture both humans and dogs went through genetic changes to make them more suited to their new diet.
Either way, now we have specific evidence that dogs are NOT designed to eat meat only but can make other stuff work if needed. Clearly dogs are designed to eat meat AND starch.
This doe not mean that kibble and only kibble is best, or even that kibble and only kibble is better than meat and only meat.
HOwever if I were feeding a non-kibble diet I'd use the above information to be just fine throwing in a few slices of banana, bits of bread, even a bit of cooked vegetables.