He doesn't say anyone "magically started out" with good taste. He's saying he had it when he started trying to get good at making his own stuff. At that point, he - presumably - had a lot of experience consuming media, and he had plenty of time to develop his understanding of what he thought was "good" and "not good". It's true that that understanding doesn't necessarily match society at large, although in the case of Ira his success indicates that it matched well enough with enough people.

Something that's not mentioned in the quote but that I think is really important is the fact that the media he was consuming in training his "ear" was - in our culture of mass-media - predominately produced by some of the very best of the very best (by some metric). Of course your early efforts are going to pale by comparison.