At the same time though, you don't buy a young horse that has really bad legs. Some minor faults can be corrected, as I said, but major things are harder. Legs and hooves are VITAL to the horse's overall soundness. In fact when I went and looked at Satin the first thing I looked at were hooves, then legs. Yes, she has her faults conformationally - like a straight back, which her daddy also has, so I don't have much hope of hers ending up with more curve to it - and yes, I bought her despite the fact that I don't personally like her sire's conformation. But I did it because she has good hooves and legs and a GREAT temperament.
Yes, you want to maximise your chances of getting that spectacular horse, if that's what you're looking for. If it's QH's, then you definitely want HYPP and HERDA negative, so yes, in QH's, you want to know the parents' genetic statuses for both, and yes, if you want spectacular, look for spectacular bloodlines.
I'm just saying, what an individual person wants in a horse depends on their intended purpose for it. My girl is intended to be a fun jumper and eventer, with some allround stuff thrown in - do I hope she'll be the next Teddy O'Connor? Of course I do! Does it mean I'll be disappointed if she's not? No way. Had I bought a filly INTENDING for her to be the next big thing, I probably wouldn't have bought my Satin. I'd have bought a foal from proven bloodlines and prayed that I got the best foal from the pairing of sire and dam. Whatever your discipline, if you want performance, you want a horse from bloodlines proven to produce great performers.
BUT - does that mean that the underdog from unknown/unproven bloodlines can't BE the next best thing? Absolutely not!