There’s got to be a chronological point where older Greek gets much easier, though. Or at least, there was back when Greeks still had to work with katharevousa in school. I learned both Ancient Greek and then, though a year spent in Greece, Modern Greek. When I pick up late Hellenistic literature like Achilles Tatius, I feel like it is activating more the Modern Greek part of my brain than the 5th-century BC Athens part of my brain.