That's a different perspective sure but I am fairly certain there is a limit for you how bad the story can get and if you hit that line, you'll drop it regardless how much you like the characters. I am not sure anyone would like to play an epilogue where the story ends but characters stay to eternity.
idk I have a pretty high threshold of enjoying things that are bad when it comes to entertainment in general ive rarely dropped even tv shows or normal games. I have yet to drop an AVN because of a bad story up to about 100 played just about now. I've only dropped a few because of the characters none because of the story. I think it depends on the character tbh for me. Someone like Charlotte I can enjoy an endless epilogue if it's literally just about them and their day to day life as long as it has romance , drama , fights etc you know stuff you would see in a normal relationship. As that's what alot of slice of life games are barley any plot and more about the romance and dating aspect. But you are right at the same time certain characters like Emma , Suzi , Lucy I would get bored or tired of it eventually as I like them but not nearly as much as Charlotte . It honestly comes down to how much I like a character I have to like a character more than normal I think.
Edit : but you are right on another front I just now realized. A bad story will never be able to get a player to care about the characters in the first place. But once I do I think the rest the story can be bad and ill like it. Like in this game I find alot of Emma's stuff a bit boring to me so I dont have any interest in her + a few other reasons but do enjoy her as a character. But Charlotte if it was never for her story of her trauma and what happened with her I would of never liked her or gotten so invested into her character to the point I can enjoy a endless epilogue. So yeah a game does need to have a good story initially but it can go downhill if im hooked to something.