I honestly don't know. Helpful af, I know. But honestly? I've seen games fail (for various players, not just me!) for all of those reasons. I tend to prefer slice of life, but there are ways that can make that interesting that we're just not utilizing.
I for one (and this is just me again) am not really into post-apocalyptic including zombies, it's a genre that bores me to watch, let alone play in (with the possible exception of The Hunger Games), and I also dislike cyberpunk.
I could go for a historical game of some kind, though, definitely. I also like the idea of a hospital setting - think slash Grey's Anatomy, maybe?
Also, I can't emphasize this enough - room for lines outside of romance. Family, friends, enemies, exes, all of that.
Just let me say ditto to this:
Personally, I like when the mods have a storyline already in place and when there is a tangible plot to get involved in. I like when there’s an open thread or two with the mods characters that invite people to jump in. Basically, an event already started that forces characters to interact and get involved. I like when there is a greater plot to the game and where the mods use their characters to drive it forward, incorporating players and their muses as they go. I love action and adventure and consider my PSLs as my slashy, romantic dream space, wherein games are about clashing of characters and IC conflict and personalities that I wouldn’t write a private line with.
Though I do think it's possible to have the romance lines in there too, of course.