For a demographically small and militarily weak nation without a Navy and separated from Europe by the Atlantic Ocean, it was very practical advice at the time just as is a father's admonition to his 4 year old child not to cross the street alone.
However, when we grow up, we quit our childish ways and make our mark upon the world.
That is true.. When Washington left the office, we had no navy or an effective army.. Now we are the world's superpower. In order to maintain that status, we have to go war overseas and enter in alliances. Times change...