I think there are two counter-arguments; first, that modern audiences find such things boring, and the emphasis should be on trendy things that will appeal to new, younger audiences, and second, that the current ranks of elite ice dancers haven’t mastered patterns and accordingly, are unlikely to excel in skating them.
And to that I would answer that first, these experiments with the trendy things have had a fair trial, but have not been successful in growing the sport, and second, fine, announce the waltz theme a season (or even two!) in advance, and give the teams more time to learn it/master it.