Not Going to Focus on Masculinity Since this is Science in Pop Culture.
"Whether one thinks it a good thing or a bad, it is beyond dispute that the culture in the 1940's and 1950's was a culture that prized pragmatism, grit, manliness, and hard-headed practicality... The culture was different. There were more boys who liked airplanes and rockets than there were boys who liked elves."
Were there more boys who liked airplanes and rockets than there were boys who liked elves or were those boys just less likely to express an affinity for fantastic ideas in a world dominated by the cyclical idea of "old-fashioned masculinity"? In America, we have a tendency to take things to excess, regress in response to that excess, and then find a happy medium before heading back to excess. Science fiction vs. Fantasy fiction is no different. Every generation seems to have a majority that focuses on one, while slighting the other, only to have the following generation take up the mantle of the "underdog" genre and pull it to the forefront while actively ignoring the other.
Fantasy seems to be the majority focus today and I think it is at least partly because of the pervasiveness of "science" in our daily lives. Science fiction requires believable extensions of current science to continue the suspension of disbelief. This gets difficult when the audience has access to new ideas from around the world on a daily basis. In the 1940's and 1950's this was much easier as everyone had the same base of knowledge and were accessing the same information that formed their knowledge of science. Effective science fiction today requires creating a new frame of science reference for the consumer that is believable, captures the imagination quickly, and keeps it engaged. That is a daunting task when the consumers all have different ideas about science and each is starting from a different place. Common ground gets difficult to find unless your science is computer/internet related, and that almost invariably leads to "artificial intelligence" and humans either enslaving or being enslaved.
Fantasy fiction also requires creating a whole framework of a world to operate in, but the consumer accepts this world as it is unfolding, there is no distraction from scientific elements that don't ring true. This framework creation explains the popularity of multi-part books and movies. Every sequel builds off of the rules and world created in the first. The tone of these worlds reflects societal fears when they are popular. Today's popular fantasy fiction is dystopian in nature (The Hunger Games and Divergent), probably due to the doom and gloom presented daily in the news. It's not too difficult to imagine a world in which the government has overreached and controls all facets of life (poorly and inhumanely). Fantasy also has a tendency to focus on the humanity of the characters, the basic goodness of people in the face of that dystopia. While the stage is dark and shadowy, the main characters reflect the highest qualities of humans. They are heroic when scared, strong in their weakness, operate from a place of love, and reach out to form bonds with those that make them better.
"I just wanted to say that I didn't know Thresh, I only spoke to him once. He could have killed me, but instead he showed me mercy. That's a debt I'll never be able to repay. I did know Rue. She wasn't just my ally, she was my friend. I see her in the flowers that grow in the meadow by my house. I hear her in the Mockingjay song. I see her in my sister Prim. She was too young, too gentle and I couldn't save her. I'm sorry." - Katniss Everdeen
"Greater love has no one than this: to lay down one's life for one's friends."- John 15:13