Saw people dunking on an IGN article talking about the recent addition of Isekai to the OED and using Frieren and Delicious in Dungeon as examples of the genre.
Of course, those series are not Isekai series (hence the dunkin' on them), but I understand why the author would think to lump in those series into the same area, because while they do not take place in another world, the world they do take place in very much resemble the kind of worlds you often see in Isekai series.
Unfortunately, I don't know if there is a good word for that style of fantasy world out there. The closest I could find is the "LitRPG" genre, but that seems more focused on the meta aspect of a series explicitly having game mechanics rather than the setting.
The kind of world I'm talking about is ones that have been influenced by the mechanical abstractions that were created to make things like TTRPGs and Video Games work.
Abstractions like: Dungeons filled with Treasure, Adventuring Parties, Adventuring Guilds, etc. These abstractions are themselves created from common tropes in classical fantasy, but then formalized and systematized in order to make them playable in games.
For example, in The Lord of The Rings you could describe the fellowship as a party, but no one would use that word in that world and it's not like groups of adventurers are just a common aspect of the world in the way they are in a series like Delicious in Dungeon.
Another example would be in Frieren the idea that there are just dungeons with treasure out there (that all look like that standard Video Game Treasure look) with magic grimoires in them is a very game-y feeling idea.
Maybe I am just unaware of what people call that type of world theses days, but I do think that is the cause of some of the continual cycle of arguing over Isekai lol.
Otherwise it's just a Sparkling Shared Frame Of Reference For Shorthand
