I'm Cis, Male, Hetero and not even through half of my 20's, so I guess I can "fit well" for the public you are aiming for.
After reading everything so far, and because I think my immature 14's self would have share some similar ideas, I'd like to give some honest advice:
I'll play the devil's advocate and say that there may be a place for harem to show in a healthy way, but all the examples of harem I've seen are just unhealthy fantasies for horny teenagers on the internet. It's not like some power fantasies that inspire you to do more, to persist and believe in yourself, but rather something more harmful and egoistic, and that makes an action story dull.
About the GL, assuming from the other comments you've posted, it seems you are just putting it there for mere fetish. Not that only us cis or men or heteros or all the latter are to blame of fetishizing relationships, but neither an excuse to do so, even more when it isn't the main story focus.
I can understand that dealing with all of the LGBT+ ideas and concepts at once may be hard to digest and even understand (more if you come from a somewhat conservative background like in my case), but at least there should be respect in disagreement. What's comedic of a genderfluid character? Or an androgynous one? You could just say you are not comfortable drawing gf or andro characters, or prefer to keep it either male or female because you still don't know how to handle other characters, or even that you fear it wouldn't be as accepted and it'd be a better response than what you said.
By no means a male looking female or vice-versa is an actual reason as to why someone on the internet would not read your story, even ignoring the people with the femboy/trap fetish, there are those who don't care as long as the story is good, or the scenes look great, or the characters are engaging.
