You could downvote the fiction tag, which might mean only fiction passing a sufficiently good filter would appear.
Although I don’t think solutions like this fully solve the general problem of people being driven away if LW gets too full of fiction. For example, it doesn’t help not-logged-in readers (I think there are a lot of those?).
This also feels wrong because I don’t think the tag doesn’t apply, it’s just I don’t want to regularly be shown that type of fiction.
I mean downvote it in your feed, which makes it show up less frequently.
Do you mean picking a −10 or −25 weight in the tag filters?