what makes a bad song? it's hard to pinpoint anything musical, as any sonic effect, with the possible exception of the children's choir, can be joyful or terrible. even datedness is not enough, as i see little difference between the worst angsty excesses of the nu-metal stuff mr. tea enjoys and pre-millennial tension.
what makes a really terrible record is the phantom listener it conjures up who actually enjoys listening to simplistic crap, someone with facile emotional needs who is easily satisfied by the least effort - who exists in the mind of the people making the tune or is even created by them - and worst of all, the horror of identifying oneself with this phantom merely by listening.