With all due respect to Chihuahuas, standard Poodles do pretty good "in the wild" and as work dogs and have a long history that doesn't involve being treated as a fashion accessory.
Also, are humans exempted from a "Darwinist world"?
Those breeds did not spring into existence from Darwinian evolution. They came about due to selective breeding by humans. Not only would they not survive without human intervention, they wouldn't exist in the first place.
(And standard poodles are actually very intelligent/capable, it's the teacup sized ones that are worthless).
And this is exactly why breeds like Chihuahua, Poodles and Labradoodles have done so well.
These types of dogs living in a Darwinist world, have no right to survive, but thanks to their human relationships they are thriving.
The big question, is this the dog wagging the tail or the tail wagging the human?