Yes, there is merit to Greek Theatre, as well as realism, because Greek Theatre is historical. There are merits to both forms of theatre, and both forms should be preserved by cultures around the world. There is something to be said for the Greek methods of using masks to present the story. It is interesting and adds to the characters.
While Greek theater has its cultural merits, much of it is very melo-dramatic and even satire that speaks to a specific culture thousands of years removed from contemporary culture. Contemporary culture like to live its theater. Much of Greek theater would no longer speak to contemporary theater audiences. So, although they are both significant in many ways, realism is more relevant to contemporary culture.