Even though 2000 years has passed in-series, it still doesn't feel like enough time for the entire world to hate the Eldians, at least not to the ridiculous extent that they do. In the original story where the term butterfly effect comes from, literally millions of years pass, and that makes what happens in the story feel plausible because enough time has gone by. Now, a lot can obviously happen in 2000 years, but we're not shown what, so it makes the entire world hating the Eldians enough to want to genocide them for something that happened two millennia ago just seem fucking insane, and stupid.