I'm using writer loosely here. It could be for video games, comics, or any other kind of creative media that tells a story.
It's an interesting scenario because, on one hand, it has to be something that speaks to you enough that you want to lift content from it. While, on the other hand, it has to be something you've given up any chance of ever directly adapting. You can't create Rebel Moon and do a Star Wars movie later on. And on that note, you can't create Star Wars and do a Flash Gordon movie later on.
I think I would borrow from anime. It's unlikely that I would ever do adaptations of Trigun, Cowboy Bebop, Outlaw Star, or Yu Yu Hakusho. I figure that I appropriate character designs, story scenarios, etc. without worrying. "Oops, I wrote a story where a supernatural supporting character has white wolf ears, but now they want me to do a live action InuYasha. I guess I've been caught at it."
There are also certain franchises that have really left me in the dust. I don't think I could hop back on the Mortal Kombat train or the TMNT train if I wanted to. And I'd have less than zero interest in doing an MCU movie unless they hit the reset button. I'm going to waltz in and write a movie that'll make a splash in a franchise that has been going on for two decades? Yeah, good luck with that.