Having character creator is extremely limiting on story writing because you have to pretend that tabula rasa is real or ignore the choices altogether

I reject this premise entirely. Several very well-written RPGs have character creators, and most of the worst stories in gaming have fixed protagonists. Certainly, it can be more challenging and more work to write a story with custom protagonists in mind, but it’s absolutely possible. It also forces a degree of (near) universality onto your themes and narrative choices, which helps with stuff like “broad appeal”.