The part of the complaining about the low level cultures and societies in isekai novels is something that bothers. I identifies with the mc here. Most isekai stories have the societies in them at way too basic of a level that it makes no sense, and in most cases it's due to the ignorance of the author when it comes to history, to medieval societies and to ancient societies.
For example, in " Common Sense of a Duke’s Daughter", the mc supposedly invent the concept of a Bank in that world. Problem is, banks are a basic concept of societies. They were already around in the first civilizations of Antitiquity, and by the Middle Ages, Merchant Guilds and Banks were common places.
Ignorance along with the myth of the dark ages(most of that period wasn't actually regressive in terms of knowledge, that's a myth propagated as a result of the Renaissance) are the biggest causes of such idiocies in isekai stories. Along with laziness(not looking up easy to look up information pieces, heck even wikipedia would've been good enough to check for most of those cases).
All of that for the sole purpose of making the mc look better because of knowledge of modern society(even though that wouldn't actually help much in realistic medieval worlds).
EDIT: and I now realize that I went on somewhat long rant about this issue... in the comments of a manga chapter that had insect reproduction as its main subject... lol