They're not necessarily "bad" but "dissonant". Most of western music has evolved through a gradual acceptance of dissonant intervals. Tritones weren't allowed hundreds of years ago, because of "the devil's interval". Major7th chords only arrived in the 20s with the great duke, but didn't reach the mainsteam until the bebop era. The more and more we hear dissonant intervals, the more consonant they become to our ears.
Really depends on the piece you're playing, and your own personal styles and tastes.
"Those who play for applause.... That’s all they get." - Wynton Marsalis
Bookmarks