I would contest the notion that harems are a necessary component of popular stories. There are multiple highly popular stories without any. I'll also note that the series you're talking about tend to just have a bunch of girls crushing on the same guy, not actually dating him. Many of those...
Yeah, gender bender written by trans people (usually posted with the transgender tag though I've seen some stories mistagged with that) tend to not have those problems. A lot of those are lesbian but that's because they're written by wlw.
This is kajarainbow signing in an alternative account because for some reason the forums won't recognize my main account. This is my first time using the forums.
I doubt 3 is quite as common as you think but comphet is a real issue in some stories, where the MC is forced to like guys even if...