I will repeat - IF it was so easy to get rid of vWD - there would not be so many dogs with it... IF you could breed out hip dysplasia - why are there more dogs with it? IF you can BREED out ALL these diseases - why are they still around?? Bad breeding? BYB'ers? I don't think so...
The # of vWD Affected dogs can be significantly reduced and eventually eliminated if and only if EVERY breeder tested and bred away from it.
And although hip dysplasia is supposed to be considered hereditary.... even if you bred OFA Excellent to OFA Excellent, that does not guarantee the entire litter will be OFA Excellent when screened. There are other variables that can affect the outcome of OFA screening (whelping problem, environmental affects, dietary affects), so no breeder can guarantee you that a pup will be OFA Excellent.
Cancers.... no one knows when this will rear it's ugly head. You could have many many generations with no Cancer issues, and then out of nowhere, it can take a dog. Yeah, lines where Cancer seems to be a regular issue, yes they need to rethink their breeding program. Besides, the carcinogens in our environment, some food ingredients... this could play a roll in some cancers as well.
There is no test for Wobblers, but again, if it is prevalent in a particular line...
DCM.... I've seen lines where they've bred a dog who sire or dam died of DCM to female who had a parent die of DCM.... YES, that is just plain stupid.
Even if you were to clone a vWD Clear, OFA Excellent, Cardio normal, Thyroid normal, CERF Clear or normal, no Cancers for 5 generations...there is no guarantee the pup(s) will have the same results on ALL of those.