How Hello Kitty takes over the world

At what point in time can we assume that the essence of Greek mythology was lost? The decision as to when exactly the essence was lost is strictly arbitrary, but when I read Greek myths as told by the Roman, Ovid, circa 20 B.C.E., I get a little skeptical as to the depth of his insight... after all, he was a thousand years,a language and a culture away from the origins of the myths... all he could possibly tell us is how Romans viewed Greek ...