I know it's easy to either forget or not care, but remember one thing making a narrative base game takes : creativity.
It's easy to say the dev only works on Nea because he might have a fetish for her and the game is thus boring, but it kinda sounds like you've never done creative writing before.
What to tell you it's not simply that the dev had more inspiration for Nea so far and thus, instead of delivering a half-assed update for every girl that would push you guys to spit on the quality, they decided to focus on the parts they had a clear vision and inspiration for, to get it out of the way ?
Also, as far as some people might despise "the trans trend", the intensity of Nea's storyline has actually a lot of potential for the MC's own character development. I mean, didn't you noticed the MC wasn't a horndog ready to fuck anything and anyone with a pulse ?
Even though I find he constant "I can't be attracted to Nea, she's not a girl, but she's a girl, but not really, but she is, but I'm not gay ?" quite infuriating (seriously the dude fights for her to be recognized as a woman and yet is the first to have a mental breakdown about the fact he sees her as an actual woman despite her transition not being fully done ?), it's not that hard to see that it's triggering quite the eye opening in him. It would definitely not be surprising that such improvement in open mindness (is that a word ?) would have influence on other routes that have, arguably, way more of an "open mind requirement" (like fucking his own sisters and probably mom at some point).
So is it infuriating that your favorite girls aren't the ones getting Nea's treatment ? Yeah, most likely, and I can understand that.
Is it something to blame the dev for, of get mad about ? I don't think so.
If you don't like Nea for her being trans, that's your right. If you don't like her for how she is, that's alright as well. Just be carefull not to imply she's stealing the focus away from "more interesting girls". Everyone has different tastes.
I, for one, really love Nea and her story. I don't think she should be the main focus, but so far, I can see how her story could serve the others ones from how it influences the MC to grow his views.
Also, please either avoid spoilers for PL or put them in actual spoilers. I haven't finished the game yet, and I would have liked to avoid those...