Though my own viewing/reading tendencies lean towards Shounen and Seinen, I have seen a bit of Shojo. One of the key things I’ve noticed is that the way the motivation is handled in regards to the protagonist is fundamentally gendered in both.
Take for example Dragon Ball Z. The main focus of the plot, Goku fighting aliens or whatnot is fueled by Goku’s desire to “Be the strongest” a common and hyper-masculine motivation for many characters in Shounen. The plot is driven by Goku’s desires, and Goku goes follows the path of the plot neatly. This style of gendered Shonen writing has been pushed even farther by Big Three such as One-Piece, where the plot cannot exist without the hero going out to seek his fortune. If Luffy doesn’t decide to go out on to the Grand Line and become the Pirate King, the plot never kicks in and there is no conflict, period.
Shojo is the complete opposite: In most Shojo, the protagonist is a woman who doesn’t want to take part in the plot but is forced to become a hero or the lead of the show. She gains the powers of a fighting girl and must fight evil, or his surrounded by devilishly handsome boys. The plot happens to her whether she wants to or not. In this way, the writer can allow her to go on an adventure without shocking anyone by giving her agency and making her appear”masculine”. An unfortunate form of writing, but that’s how things tend to.