I think rising prosperity explains the increasing differentiation of toys by sex, as explained in this essay by
Steve Sailer:
poor societies tend to be less sex-differentiated in many ways than rich societies simply because they are poor.
It's pretty much basic Maslow Hierarchy of Needs, with survival at the bottom and self-actualization at the top. In 1900, a nice Christmas present to find in your stocking was an orange. You and your sister both liked the oranges your aunt brought you in 1897 and you've been dreaming ever since about having another orange. Their sweetness showed they were providing needed calories. Oranges even had vitamins.
A century later, you and your sister have, to be frank, more calories than you really need, but their is no end to your feeling that you need more self-actualization via fantasy, so your sister is demanding a Polly Pocket Fairy Wishing World, while you are throwing a tantrum over how much you want a Power Rangers Samurai Bull Megazord Action Figure.
...
All else being equal, manufacturers don't want to sell more versions of the same thing, they want to sell fewer versions to keep costs down: "You can have your Model T in any color you like, so long as it's black." They provide more versions because of demand: i.e., boys and girls tend to like different stuff. Just as General Motors outmarketed Ford in the 1920s because Alfred P. Sloan figured out that the country was getting prosperous enough that there was a new mass market not just for the basic transportation Ford's Model T provided, but for allowing customers to self-actualize through car purchases by providing a variety of levels of luxury in cars in multiple colors and with changing fashions in sheet metal, richer societies sell more ostentatiously masculine and feminine toys and entertainment.
