Yes. Fandoms are awesome and cool. But I'm not talking fandoms.
I'm talking, a parent comes into a book store and asks for a book series for their teenage kid to read. Parents of girls are much more likely to get handed either the Hunger Games books or Harry Potter, while parents of boys are much more likely to be handed just Harry Potter. Girls get advised books with both boys and girls as main characters while boys are much more likely to be handed just the books with boy main characters.
It's not even fair, not on either of them. But there is this idea with a lot of people that male main characters are relatable for "everyone" while girl main characters aren't, they're just relatable for girls. It's stupid, stupid as hell.
And yes, it's changing, mainly because of the awesome fandoms. But in publishing, in big publishing and media companies that make our TV series and films? They still think like that, at least, too many of them do.
This does not in any way take away that we need boys and girls and non-binary and everyone else in our stories, that we need well developed and awesome characters. Not cardboard cutouts, not stereotypes, not "token" characters who are nothing more than a prop for the main characters to show how 'inclusive' they are in their friends.
We need as many different female charachers as we have male characters, and just as well written. You don't have to write either a well-developed white-straight-male or a not-as-well-developed other character, you can have well-developed black girls next to your gay guy and your transgender hockey player.
But we do have to challenge this idea that it's either/or. That you can't write a relatable story about a subject just because the main character is a black girl.
Representation and diversity in your fiction (and not a saussagefest of 9 men and 1 token woman) is important, because there are so many more beautiful people in this world, who barely ever see themselves in fiction because white-straigh-male is the "neutral" character and anything else is "added baggage". If you want to only write one type of character, that's okay, that's up to you, but maybe ask yourself why you do it? Why you're only writing one type of character when there are so many cool people out there?