But representation is super important. It's so empowering to have a character that resembles you in media. And they have to be in a main role, they can't be secondary characters.
Essentially, all they're doing is self-inserting without the hassle of creating a new character for themselves. They've learned through all the progressiveness that, if the character doesn't have anything relating to your personal race, sexuality, or whatever you identify as, the character should be headcanoned that way. The unfortunate side effect of this is that, when they do bother to create their own characters, their whole identity relies on race, sexuality, and what they identify as. The very concept of a character standing alone as an actual character with flaws and a personality that's not cardboard is dying a slow, agonizing death.