American have altered most pure breeds to the point of destruction. Most pure breeds have some genetic maladies. Shepherds, Rottweilers, and many large breeds tend to hip dysplasia. Chihuahuas tend to be aggressive because they have been breed for a large cranial dome. Dachshunds and other long dogs tend to have back problems.

I have had dogs for most of my 70 years and have always had better luck with with mutts.