I think one of the traits of a dog with a good temperament/genetics is not being easily traumatized by bad experiences. My dog has even been bitten(not at a dog park) and he didn't develop any behavioral problems from it.
Not all dog parks are bad. I've personally never been to a dog park so small that I experienced what you described. And it sounds like bad owners and bad advice are the main culprits, not dog parks.
Dog parks helped me eliminate the leash reactivity in my dog when absolutely nothing else worked and some minor resource guarding. Now he won't even react on leash when another dog is reacting within mere inches of him, and he freely shares his toys with other dogs.