I wrote a big essay that was basically what you already said, only with way more pointless words. But it was kind of pointless and didn't say anything, so I deleted it.

So instead, I'll talk about my own experience with these sorts of people. I often draw art for the sort of people who are the prime target for isekai stories, and they are just generally very poorly socialised. They often have a poor understanding of boundaries or what might make other people uncomfortable. They're usually not terrible people or anything, just lonely guys who struggle with human connection and have found a quick and dirty "diet" version in the form of parasocial relationships with their favourite anime character.

So yeah, the problem is dehumanisation under capitalism.