Akainu literally says he doesn't know the military there. He says the borders are closed. He literally says he has no idea what the hype is about wano. And he literally mentions that kaido is there. Ain't gat shit to do with ryumas Legend
Ryuma legend is one of the reasons samurai are feared - a single samurai who fend-off the whole world? How do you think people outside of Wano view this? How do you think this effect their opinion on Wano?
Same with Kozuki Oden who made name for himself and Is extremly strong.
Most people know Wano for the powerful samurai not for the fodders and it's hard to guess what the power of the countrh however the mere fact monsters like those seem to keep appear from Wano give a good reason to be scared - and Ryuma as the WSS of his peroid who achieve by far the mlst is a big part of those rep.