"Good dance music is played by musicians who know how to dance."
A nice piece of observation, though I think I prefer:
"Good dance music is played by musicians who watch the dancers dancing and play accordingly."
While I don't believe that having two left feet should prevent anybody becoming a good musician, I think an understanding of the root of Irish traditional music, the dance, is essential to good playing.
By the same token, I agree totally with a comment made regarding Seamus Ennis's playing, "Those who understand singing make the best slow-air players".
Jim Carroll