I will go with 'ruined'. There have been a lot of breeds who have been saved by enthusiasts who did not want to see the breed die out. Rarely did those enthusiasts pick up the breed simply because they wanted to show them. Usually, they actually used the breed for it's intended purpose.
What usually happens, is someone down the line will get involved in saving that breed, then they brag to their friends about their 'rare' breed of dog, that they are SO expensive because they are SO hard to find and of course they are a wonderful breed, just perfect! Because, if you are trying to save a breed, you have to breed a lot of them, and you have to find homes for all those pups. Sometimes, they end up in not so great homes.
Then the backyard breeders start seeing money signs and start pumping out the rare breed so they can make a lot of money!
Meanwhile, the responsible breeders who wanted to save the breed in the first place realize that they need to get the dogs into some sort of registry, so they can be respectable. They open a stud book and start some sort of program where they can track all the pups that are now being produced. They create a Standard, so that they dogs can be measured against it, trying their damndest to instill into the standard every nuance that makes their breed unique.
But, once a standard and a stud book are established, here comes the folks that want to show and create the 'perfect' dog. The enthusiasts work hard to keep the breed true to their function, but the 'show only' folks concentrate more on form.
Then, the death knell... getting into the BIG registries, like the KC, CKC, FCI or AKC. Those registries could all do ONE big thing to save the function of the breeds. They could require that, in order to get a Championship or Grand Championship, the dog MUST have a title that proves they can do the job they were bred for, if that job exists. Hunting dogs should have at LEAST a Junior Hunter title. Herding dogs should have a Herding Instinct certificate. Sighthounds should at least have a Junior Courser title. Maybe Grand Champions should also have the more advanced working titles.
But, it will never happen, because the big registries are all after money, and they will get less money if anything excludes dogs from the shows. And believe me, MANY show dogs would not be able to get even the basic working titles out there for their breed.