The worst part of some isekai is how they make other worlders dumb. That's just grilled corn on a stick, nothing new there, any idiot could've figured out; you didn't need a modern day isekai protagonist to discover that. I Googled popcorn, that shit is cool and all, but it's also 5 thousand years old, that medieval society could've figured that out by themselves.
It's all in service of making a power fantasy where modern day Japanese people's common knowledge is seen as vastly superior. It implies different cultures, like native cultures, are vastly inferior. It's a colonialist power fantasy. It underestimates the power of human intelligence that is still present in less developed societies. It reinforces a false conception of humanity, society, technology and history. In other words, it's pure ideology. (it would be so easy and much better if it was different)