I'm sure a cis author who writes a gender plague story, if they think of trans people at all, just desperately want to be able to say "Okay but pretend trans people didn't exist for a second because my story is really interesting!" and that mindset in and of itself is the problem.
Whatever revolutionary idea you think you have about gender that can be explored in an interesting way in a cis-exclusive story about how all the women or all the men were wiped out, I promise you that queer people are already exploring this stuff.
I don't really know what the answer here is either because in theory a gender plague story can be written where trans people are considered. You can even make it magically able to read a person's inner gender and make it not about killing trans women with cis men, for instance.
But I wouldn't want a gender plague story that remembers trans people exist to be handled by a cis person. It would definitely be mishandled.
So ultimately maybe just fucking don't?
Like I can just hear the implicit "Oh gosh what would people with vulvas do in a world where some of them had to be men???" and it's just like, go home, cis people, adults are talking.
Cis people, even a lot of the accepting ones, seem as though they think that trans people are this thing that happened to gender, like it all made sense before we showed up and complicated things.
So I'm sure it's tempting to think that you can talk about gender without considering us or adding us in as an afterthought.
Cisheteronormativity is the the actual aberration. That's what's unnatural. So when you break down those barriers, even in a thought experiment, what remains is wisdom we as trans people already have.
You as a cis person have discovered nothing that wasn't previously known.
Anyone who starts to untangle gender like this is going to make missteps. That's normal.
But it's worse when you're a cis person for whom this is all fantasy. Then you might not learn the real lessons you should.
In short, you cannot separate us as trans people from a discussion about what gender would mean in a world where suddenly what's understood as the basic tenets of gender are removed or reset.
That's already our life.
(And no, trying to be "biological" about it and claiming your virus killed everyone with a prostate isn't solving anything even if cis women didn't have prostates [which they do]. You're just repeating violence and transphobia against trans people that already exists.)
