In China, women over 30 are described as left-over. See https://en.wikipedia.org/wiki/Sheng_nu . The term brings to mind products left unsold on supermarket shelves.

As you probably already know. In Japan, women over 25 are called Christmas Cakes. See https://en.wikipedia.org/wiki/Christmas_cake#Japanese_metaphor . It similarly references cakes that are unsold after December 25th.

There is no equivalent term in the west, despite common sense that women over 30 simply has no advantage over their younger counterparts. What happened to the culture?