Life wasn't easy for us anime fans 20 years ago, and it wasn't just because people heard that you liked something called 'Outlaw Star' and instinctively wanted to cram you into a toilet.
I'm not saying that a girl can't be the hero of a story because human traits would make her too fragile or weak. I'm saying that in these specific plots, the characters would totally act and react in a different way than what we got.