Take the legends that swirl around old masters. This one could kill a bird with his kiai, that one could defeat whole armies and that one could actually fly.
Of course those are exaggerations...a bit like the stories of masters.
Yes I’m sure they were excellent martial artists and had profound knowledge of their subject. But as I’ve yet to see a master of today actually fly or be employed as a country’s secret weapon (although maybe he exists as I wouldn’t know it being secret!). Nor have I ever read of one that could defeat armies in any other periodical other than Captain America.
Although they might have more knowledge I think the past master would often struggle against modern fighters simply because of modern training methods. They were, after all, only humans...