Female superhero movies could actually work and they're not inherently contradictory with the hero's journey,

They are contradictory for the fact that a man has to build his worth to overcome adversity to eventually establish and generate a worthwhile legacy and lineage.

This is not something a woman has to do ever, she simply has to find a man she genetically feels predisposed to create a lineage/legacy with.

So a female superhero is literally antithetical to the hero's journey because of what current_horror said: a woman's greatest trait and virtue is something she's born with, hence her inherent value is what she has to GIVE not what she has to achieve.

A man has to ACHIEVE his value to receive the gift of purity from a woman to create an offspring based on his stature as a hero (his achievements change him, and thus make him worthy of having a strong seed). That's the whole point of the hero's journey: that a man EARNS his right to a legacy.

Women don't have to earn anything, and there is no reason for them to because biologically it serves no purpose. A female superhero can work, but not in the same way as a male superhero, which is precisely why most female superhero films simply do not work.

The only one most people consider to be relatively "good" was the first Wonder Woman, but keep in mind that she didn't have to earn her worth; once again, she was born with it. So no hero's journey there. The same thing with Red Sonja -- who had her value forcibly taken from her and so her journey was one of revenge rather than one of attaining value.

The end goals are always going to be different between men and women due to base differences in biological essentialism. This is precisely why the hero's journey for men is so much more compelling than one fabricated out of absurdities for women. Because in the latter case, we all know for a fact how basic biology works and how the dating market works, and how Western societies favour, pamper, or coddle women. So trying to depict a woman struggling like a man is both unrealistic and subconciously jarring because we all know it's not true.

For women, their stories are always more compelling when it's centered around traits that identify with their real life struggles from a feminine perspective, typically dealing with familial issues, finding the right romantic partner, or seeking restitution/recourse/retribution for a grave injustice (the last of which actually applies equally to both sexes for obvious reasons).

If you look at most good films that star women, it's usually about some form of recourse for what value they've lost, rather than what value they can gain. As opposed to most good films starring men, where -- as current_horror points out -- the hero's journey is always the more compelling narrative for him.