The little show in the atrium was originally meant to stagger the muster drill check-ins. They would space families apart for the little show while the previous group of people went to their muster stations to do the modified drill, then they could go off on their own. At some point they kept doing the little show but stopped escorting passengers directly to the muster stations, and now the show is also gone.
I'm not sure if it was meant as a direct replacement for the sail away party, but I believe the big party is back on all ships.