I'm certain there are still good working stock Aussies if you head out to cattle country. But, once they became "recognized" as a purebreed and AKC got their hands on 'em, they became an overnight sensation. Now everybody just has to have one.
Puppy Mills: The rate of deafness, blindness and hip dysplasia is just soaring. Catahoula's seem to suffer from the same deficits: there's a Merle gene, which when crossed produces many of these problems.
And, as to all breeds: we no longer "cull" the way we used to. Catahoula breeders in LA were notoriously cold-blooded about this right up until (and in some cases including) today. It's a philosophic argument that I'm glad I don't have to partake....do you kill weak puppies in the interests of preserving the breed?