Soooooooooooooooooooooooooooo, lets unpack this a bit. Its not really wise to write for all demographics. there it a reason why this is divided. People are vast, but can be categized in many ways. Unfortunately, marketing is very sexist and has been that way for along time. As a woman, I can't tell you how much I hate baby commercials. But, the reason why these are divided is so you can narrow down your audience, and not spread your recourses thin. Many corporations do this and for good reason. If you want a general demographic, try family friendly. This will pull in kids and some adults (this could arguably be one of the biggest demographics). But when choosing your demographic, you can choose to target a gender group, or you can keep it gender neutral. So you want to target a sexual orientation? etc . . .
In my story I choose to write for action fantasy. I do not pander to one gender or the other, though some might argue that action is more masculine orientated. In keeping it that way, I include what people so in the real world. So, yes I do portray the male gaze, or the female gaze. I also do not sexulize characters for the sake of appealing to an audience. The few characters I do, do that are ones who are ok with it, as if they were people who enjoyed that kind of attention. No shy busty girl who pines over senpai ibn clothing that she is uncomfortable in. If anything I very much dislike tropes like that. The way I see it, is that the characters are their own, and I have no say in their story. I write as if they are doing what people do, without some target audience in mind. I personally write for myself, and those who share the same interests. I hope that makes sense.