Why do some people give great importance to the breed of dogs, while the dog is a dog?
You will never, ever see a Newfoundland herding sheep.
You will never see a Yorkie hauling a drowning swimmer out of the ocean.
It would be absolutely impossible for a Mastiff to join a sled dog team and run the Iditarod race.
No Pekingese can possibly join you as a jogging partner.
Although all dogs are individuals and individuals within a breed vary quite a bit, breed still matters. It matters a lot. Somebody who is very happy with their Viszla is not necessarily going to be happy with a Belgian Sheepdog, even though both breeds are excellent for the right person.
Purebred dogs are predictable, within limits. Those limits are, however, fairly strict.
Random-bred or mixed breed dogs are predictable only within MUCH broader limits.
If a person wants certain characteristics in their pet, and almost all Papillons fit those characteristics whereas no Akita in the entire world ever has or ever will, then that person should get a Papillon. Even if that individual dog is large (for a Papillon) and quiet (for a Papillon) and stubborn (for a Papillon), it will be small, yappy, and willing compared to any Akita.
And that is why many sensible people decide what they want in a dog, research breeds that typically show those qualities, and get a dog from a breeder who is trying to propagate those qualities in her personal line. It beats throwing a dart at the entire universe of dogs and hoping that out of the millions of dogs out there, you just happen to get a dog that fits your personal preferences and needs.