With the advent of online dating, women in prime reproductive age are in the dominant position in the dating market for the first time in human history. This comes with huge social ramifications. Setting aside local and recent context, dating has historically been drastically riskier for women than men (and it still is, but less so). Physical safety has been an ever-present issue for women in meeting potential dates, not to mention after agreeing to be alone with them on a date. In the era of online dating, women are at significantly less risk simply by not being in the immediate proximity of their prospects, and rejecting a prospect has no downside risk. Women globally also have more upside potential because they can draw from larger prospect pools than ever before. Due to the significantly higher biological risks associated with reproduction, women are intrinsically far more selective when evaluating potential mates than males. In an online dating context, this selectivity is more apparent than ever, with significant knock-on effects for the rest of the culture. There is less pressure to "settle" than at any other time in modern history because of the availability of alternatives and the speed of interactions.
Personally I think this all goes back to economic changes that make it easier for women to support themselves; online dating wouldn't matter if women still needed a husband to support them.
But I suspect it is true that 1) women are in the best position ever to be picky about mating, and 2) many young men are just not what most women are looking for.