Most purebreeds are genetic backwaters now with large numbers of congenital defects endemic. Dalmatians being born blind and having seizures being an obvious example.

Then when you add on the characteristics demanded by kennel club “breed standards” you end up with frankenstein creations not able to support themselves. Daschunds with legs so short their belly is constantly rubbing on the ground and they get infected sores, bloodhounds with such drooping jowels that they get injured, bulldogs that can’t support their own weight. Mongrelise your pets!