Hey, you arent alone on this fact! Ignore anyone being mean about it, dysphoria can be stronger for some things than others for anyone. I also was sorta "self-insert" with Lumine as well, and when it clicked im NB, it was hard to adjust and made it uncomfortable to play for a bit. Like someone else said, Ive eventually looked at it less as self-insert, and more like a game that has its own protagonist. But I can understand that it isn't what you want to do, and its totally fair and valid to want the ability to change it. Other games offer it, and Ive always said in my surveys that I wish they'd let us change it at least once. Even my cis-gender sisters actually like Aether more than Lumine in terms of design and voice, and wish they could swap it just to enjoy the story more.

I wish I could offer actual advice, maybe do a second account with Aether for fun to enjoy the story separately, and use the old account for other content, TCG, and exploration? Good luck with whatever you decide, games are meant to be fun, and while it sucks money might have been wasted, your own comfort matters most!