i couldn't put my finger on it, but as i gave it much consideration for a few years (no joke, i've been consciously trying to dissect it for some years, but it's been in my life since probably around age 8). i think i narrowed it down.
my testing was "how do i feel about the following":
eyes: huge, weird, alien, buggy, strange. anything but gooey sappy anime doe eyes. i decided harsh, glowing weird spooky eyes with a fierce gaze does it. more abstracted soft eyes, that turn fierce and melt steel beams - yes please! i like some shifting and tensing or loosening!
mouth: decided i dont' really like that part. yeah so it's an orfice you could jam something into, but i prefer those things be hidden. seeing mouths just makes me see them like furries/humans/ "too equal". idk. haven't figured that out. abstract pseudomouths are good.
ears: not mammalian. robot, weird, alien, sure. just no mammal ears. otherwise they'll look furryhumanequal.
male/female/?: doesn't matter. i just like thin, toned, fit. no more than SLIGHTLY chubby. i like muscles tensing and relaxing.
no boobs or visible male parts. those are too humanfurryequal. like mouths. if i see them, my brain goes "oh it's just another human being, fur and tail optional".
- uhhh i'm weird about attraction, which is odd... i guess you could say my weird brain thinks humans as a whole are "sex A", and bizarre weirdo abstract people are "sex B", but i don't want to knock them up. in fact i find it unattractive if they can reproduce, that would make them like humanfurryequals who get married and start families and cheat on their spouses. i'm not into commitment, i don't fantasize about marriage and families. i just get hot and horny and want to overpower and fuck the brains out of an object head if they hit the right notes. probably with improvised tools, and turning the immediate area into a sex dungeon.
then i'd let them go.
i respect equals too much. no attraction.