Demise's "curse" is nothing but an infantile attempt at connecting the games together, one which should never have been made. See my above comments about Prequelitis.
It also does the character of Ganon a grave disservice, by rendering him nothing more than a second-rate reincarnation of some other lame villain we'd never heard of until now. I call BS on this—Ganon is far too cool and badass a character to be written off in this way.
The way I see it, these kind of dumb story elements, as well as the annoying gameplay, mean that Skyward Sword isn't actually a real Zelda game at all. Dismissing it altogether ensures that the perception of the other, far greater games in the series is untarnished by its nonsense.