It's probably safer to lower this one's ranking, rather than absolutely block it. There's more than a handful of things for which fandom.com is the correct result—the only actively-maintained wiki.

Trust the search engine to do the signal/noise calculations for you. You are no longer on Google. Kagi is your agent, not your adversary.

There's an add-on called BreezeWiki which redirects you to an annoyance-free mirror of Fandom sites, which makes it at least a little less annoying to visit those wikis. It can also redirect you to a community-run wiki if it exists.

I found it through Libredirect which is the same idea but for more sites, but some of the alternative sites don't work as well in my experience.

And while Fandom/Fextralife are both irritating sites, they often are the only way to get a certain bit of knowledge on a topic. They've kind of moved into the niche previously occupied by things like Geocities fansites. They're nasty, ad-riddled experiences, but they DO have the information.

Only sites I block on my Kagi are sites that outright trick or lie to the user; keyword content farms, pinterest, and StackOverflow cloners

I have fextralife in my lower list. As you say, sometimes it's the only place. But when there are any other places, I want those in front.