Isekai, different world, became the standard genre tag in the 2010s web-novel and light-novel boom, the 'reincarnated in another world' pipeline. The word is new; the device, ordinary person crossing into a world with different rules, is as old as the stories.
The old story: the fisherman Urashima Taro rides a turtle to the Dragon Palace under the sea, stays what feels like three days, and returns to find three centuries gone and everyone he knew dead. Given a box he must never open, he opens it, and his lost years fall on him at once. Japan had another-world fiction with time dilation in the 8th century, before the trucks started hitting protagonists.
The claim: isekai is Buddhist samsara streamlined for content platforms, death, rebirth, karmic stats, only now the sutra is a status screen. The darker extension: the genre exploded in a labor market where the core fantasy is that your abilities transfer to another world, because they visibly do not in this one.
If the dominant fantasy of a generation is that your skills only matter in another world, what is the diagnosis of this one?