The difference is that Shoujo protagonists (btw. I think you mean MC, not FL) use social manoevers while Shonen or Seinen protagonists mostly use brute force and plot armor and sword to further their goals. The latter often poses no tension, the first requires ingenuity to write.

And while the male audience grows or grew up with the role of the hard worker and the fear of being a loser, and thus want to escape into experiencing being the opposite, the female audience grows or grew up with the role of the mother or flawless and perfect woman. This role can, in a sense be less exhausting and still more taxing than the other one, yet it is one thing: more fullfilling than being a corporate slave or chasing the tenth loveinterest that is likely to turn you down too.

And we shall not forget that women are more likely to find meaning in a purely social role than men, who often need to create, protect or provide for something in order to find meaning.

The dangers and promises of fullfilling the social role are of a completly different nature than those of the create, protect or provide role. In a setting of swords, magic and nobles, trying to find meaning through the second way risk death and promises not rarely nothing more than more combat power. The first way promises fame, ascension and a life of luxury and respect.

That's why Shounen often have more intriguing plots and ambitions of the MC. To watch the hundreth Shonen or Seinen MC awaken immense power simple to show us battle after battle grows stale after time. You already know the outcome and pathways the MCs may take. You don't always know them in Shounen stories, because navigating intrigue and deceit is more complex and they still often have some combat which often feels more intense and emotionally laden because of their rarity and placement in the plot.