I don't think the line dancing creates any significant delay. I ref U15s sometimes with no lifting and no dancing, and I can't say that lineouts take significantly less time.
If there is some delay, it's not much, and it's worth it as I think lineouts are actually a fun and vlauable part of the game, both for spectators and for players. It's no coincidence that the statue outside the stadium at Twickenham is a line out
