1. Common sense, do you think people who lived in 5th AD are physically significantly weaker than people of current
2. If those people are fodders, no point for Ryuma's hype in the eyes of Wano citizens
3. Math, he fought literally everyone of the outside world, by probability, he must had faced 1 or two Top Tier given he fought literally everyone of the outside world, plus Wano is in New World after all