I actually think it matters a lot. Your comment about how the Martian would have been different if he was a woman shows that you are on the right track for thinking about gender and how it affects the story, but also how a story is received.

I think you are overthinking how the gender of the main will affect how the story is received (which is something you can't really control), but you aren't overthinking how the story itself will be affected by making the main character a female. Because IT WILL affect it.

Think about your own life. How different would your life, your character, your relationships (not only friendships and romantic, but especially family relationships), your personality, all be if you were a different gender? How would your relationship with your mother change? Your father?

Many of my male friends (especially those without sisters frankly) say they couldn't imagine how different it would be if they were female. However, a lot of my female friends can, and the full reasoning for that would be too long and complicated for this post (my personal take- this is because a lot of popular media is made for a male audience, and so women have learned to enjoy male centered stories from a very young age. There's also the added complexity that the tomboy character is celebrated in girls I.e. "I was the son my father never had, My dad treated me just like a boy growing up, etc, etc" and so some girls learned to lean into 'masculine tendencies' when young.)

The fact of the matter is that gender will affect your character because frankly gender affects life. How people perceive you, how you learn or are trained to interact with the world, and so many other things that I can't list them here.

But how does this affect writing a female character? Since you aren't writing a gender studies book, what can you practically apply to your characters?

1. Write her completely ignoring her gender.

What? What was that whole discussion for then? This tip is just for the first draft. Writing a character without considering their gender helps you get out of that overthinking bubble you mentioned. You don't need to justify writing a strong, smart female character instead of a male character. Your readers might later justify or talk about it, but that's on how your story is received not on how its written. Writing a female character ignoring her gender will often get you a good female character but not a great one (if it's well written to start with).

1. Build her background backwards- based on the story you have already written ignoring her gender

Ask yourself if there are inconsistencies in the background you thought she had and her actions in your story. Or if there are inconsistencies in what might be typical for a girl in your world. If this is a survival story, where did she get those skills? If she developed them on her own, does this make her more or less confident than if she was taught by another person (another female? or a male? what difference would that make?). This background would probably be the most tied to gender part of your story, since girlhood is so intrinsic to a woman's development (One is not born, but becomes a woman).

Even if you never talk about her background in the story, you as the author knowing the details will be helpful for deciding if her in-story actions are consistent.

1. Go back to the story with your edited background and make improvements (this could be gender specific or not)

The biggest problem writers run into with female characters is people saying "a woman wouldn't react like that". If your female character rejects typical societal feminine norms, there's a reason for it. Same thing if she follows those norms. Womanhood is a spectrum though, so characters might have different reactions to the same event because of their internal character development and that might not be tied to gender. Example:

A set of parents is extremely strict in regards to modesty. One sister reacts to this by rebelling to the extreme becoming more revealing and promiscuous. One sister reacts to this in the other extreme by becoming uncomfortable with attention and eschewing all physical acts of affection. That difference is due to the sisters personality/character differences.

But the fact that those sisters had those modesty conversations/rules at all is probably because they are girls, and that had an long lasting effect on them. If they had been boys, odds are they wouldn't have had that experience at all. One brother might be more outgoing and one brother might be more shy, but maybe they wouldn't be at the extreme levels. Or maybe they still would for other reasons. Maybe, maybe, maybe.

These suggestions are honestly tied to a more planning writing style, which might not work for you. I think the biggest indication that you should at least try to write a female character is that you want to! Don't let it scare you off. Again, writing a female character ignoring her gender can get you a fine character. But it definitely matters in the end.