Isekai operate on two levels. First, we have the experiences of a modern person. Second, new rules and experiences in the fantasy realm. The main character is nearly always rewarded from the new environment by experiences in the old world.
Isekais seem to argue that a competent Japanese office worker or student have the intelligence and drive (with a bonus) to make it in another world. These are worlds of adventure that lack today’s politics and bureaucratic structure.
Clearly, after some initial shock, main characters make the trade. It’s pretty rare that characters want to return to the old world, often it is not an option. Instead characters remake some part of the fantasy world in the image of the modern world; utopian politics; aesthetics. A dream world.
It is a world of remarkable freedom rather than imprisonment. There are exceptions to this rule and in those cases the main character does not get an overwhelming resurrection bonus: it is not complete fluff.