What differentiates a period piece from a dated work? At first glance, quality might seem to be the main difference, but it’s not. For example, Getting My Act Together and Taking It on the Road is an excellent show but it is definitely dated. Lack of universality might lend itself to datedness, but the while Moon for the Misbegotten is not universal, it is also not dated. Perhaps being too contemporary is a problem, since some of the most cutting-edge pieces are the most quickly dated, as time blunts their edges. I suspect the answer to the period-vs.-dated question is probably a complex formula along the lines of
“breadth of the moment examined” + “deepness of the examination” - “level of reliance on contemporary signifiers (brands, TV shows, etc)” x “talent and insight of the creator(s)” + "number of years from the present time"For example, Getting My Act Together examined a particular moment in feminism, and feminism‘s success is one of the main reasons it is now dated, yet A Doll‘s House isn‘t--perhaps because of its underlying themes of loyalty and trust. Also, the Ibsen play is over a hundred years old, allowing the audience distance, while Getting My Act Together is only 30 years old.
The new musical version of Vanities, adapted by Jack Heifner from his 1976 play, is dated. While the ins and outs of friendship and loyalty are universal, this particular story depends on now-cliché tropes that limit its story to a tiny time and place. The new version has nothing new to say, which might be okay if it said the old things better. The three actresses give it their all, and there are moments that work, but mostly it just isn’t particularly interesting. The songs add little to the mix.