>>6300250Isekai is just the new Jap term for "portal fantasy". The main issue with the genre is that it was almost sort of invented to be more believable than a "high fantasy" world, and it was very common with children's literature last century. Like Narnia, or that one with the castle in the attic you could shrink down to. In a lot of ways it's kind of an outdated genre because people have moved beyond that type of literature where they can only self insert with a believable method of entering the fantasy world though it is still obviously very popular in YA fiction even today (Harry Potter, Homestuck, etc)
The main issue with the genre I think is that it doesn't really do anything on its own to stand out. You could just have a story where a character is of a fantasy race or has some circumstance that would be the center point of an isekai story- like the "I got reincarnated as a lvl 1 spider mob in a VRMMO?!" You could just set the story as being that character in the first place, unless you have a really interesting sort of thing you want to explore with the characters internal dialogue being reincarnated in some new world as contrasting the real world. But this type of writing Challenge and exercise is much less common or less popular than just total wank off the MC either morally or intellectually using their Real World Knowledge and experience to cheat the game and beat everyone and everything and get their wish fulfillment of not being a loser in the real world, like solo leveling. The one Saving Grace of it is that it is very much a internet or web adjacent sort of genre that is perfect to explore in a quest format because it's so interactive as opposed to like a novel or anime or something that's just created and consumed. If you do want to do an Isekai story with a weird gimmick, this is basically the perfect place for it.