My wife thought the same thing until we had a boy.
While the range of enjoyment varies more within the sexes than across the sexes, in general, left to their own devices, girls will gravitate more towards traditional "girl" toys, and boys towards traditional "boy" toys.
Girls can (and do) enjoy lego, but they don't gain satisfaction from spending hours of time alone building towers and space ships. Boys will play with dolls (okay action figures), but not to the extent that girls will play with Barbies.
In our household, we base our decisions about what toys to buy based on what the kids actually play with when they get their hands on it. Most parents I know do pretty much the same thing. Most families have no time or energy to worry about the politically correct issue of the day.
My daughter was considered a tom boy. She often preferred playing with the boys to the girls, and had a selection of both "boy" and "girl" toys. Later, my son inherited many of her toys. He plays much more with the trucks and transformer action toys than she ever did, and not at all with the "girl" toys that still survive.
Disney has not been able to break into the aftermarket for boys nearly the way they have with girls, and it's not for a lack of trying. Girls are eager to dress up as their favorite princess, but boys in general have no prolonged interest in dressing up as this or that pirate or prince.
In the mid 2000's Disney commissioned an anthropologist to study the culture of boys. What they discovered was that boys, as a whole, have an entirely different type of culture than girls, within the same macro-culture. See Link
Based on that research they had to invent a whole new marketing machine from scratch to reach the boys aftermarket. They went so far as too buy marvel comics and Lucasfilm (star wars). Yet they still have not been able to establish a solid aftermarket product that is particularly sought after by boys.