I mean, I do think that cultural details are the hardest things to get right -- but if you are going out of your way to put in a plotline about something specific, like a particular kind of visa, or a particular work of literature, or a particular ethnic group, or a particular philosophical worldview, that's a specific set of information that isn't too hard to find out! (I don't actually think that you need to have read the Iliad scholia in order to have your characters in a novel set in the ancient world read Homer. But I do think that you should know what the narrative of the Trojan War was.)