They didn't even allow black players to play against him. Also, MLB was kind of a joke for a long time. NYY, Dodgers, Giants were like the "Majors" and many other teams played and ran themselves like developmental teams. Ruth was fat, couldn't run.
It is a similar argument as like taking a basketball player from the 1940s or somethng (Ruth much earlier obviously) and saying he is the greatest ever. There is simply no way Babe Ruth is the greatest player ever lived.
Also, he might be just a legend from the past anyway (like Jesus) Not sure if he ever existed for sure. /sarc