When you build a new land specifically to anchor an IP-related attraction, you are in effect creating a land around that IP, even if you drop in side/smaller offerings that aren't linked to it. If you want to split hairs about the specific terminology, fine, but my point remains the same.
I wouldn't call New York the "Jimmy Fallon Land." I wouldn't call Hollywood the "Bourne land." I wouldn't call Epcot's Paris the "Ratatouille land." I could go on.
Seoul would be created as an eastern anchor, similar to other city based lands at USF (with London being the exception). As I mentioned, they could easily add IP that would fit with this general geographic region. Kaiju, giant robots, martial arts, cyberpunk / futuristic themes all could work for a Seoul land. Avatar The Last Airbender, Pacific Rim, and many other IP which reference eastern culture could fit there as attractions. (If kids aren't criticizing K-Pop Demon Hunters for not being genuinely Korean, I doubt they'll have any issues with other IPs in this land.)
With the entire land not relying on the success of a single IP, they could change the IP of the attraction(s) as needed without having to demolish an entire land.
This idea relies on Universal building a really cool non-IP land, instead of going all in on a single IP.
I'm not saying this is my top preference, but the reasons this doesn't work really comes down to A) a misunderstanding or misrepresentation of the concept ("splitting hairs"), B) assuming Universal will never build a non IP focused land (which is likely true), and C) business deals falling through / not getting appropriate IPs to tie into the land (which is also valid).
My preference would probably be Tokyo, with the same general concept of non-IP based city with blockbuster style attractions. But I've seen that suggested already, so
I thought I'd offer something fresh instead of arguing about the merits of Shrek for another few pages.
As far as the K-Pop Demon Hunters IP itself: Universal almost surely agrees with the rest of this forum... Too early to build an E ticket. But
I think the IP is worth keeping an eye on. Yes it's early for this IP, but we're also talking about rides/lands that might not open until the 2030s.