To what extent is it true that Shakespeare’s Macbeth is a timeless play that continues to hold value for modern audiences?

Shakespeare's Macbeth still has value for modern readers because it addresses, in part, human nature, and human nature is timeless.  Yes, it is about a man who does a number of terrible things in order to acquire and retain power, but this is not really what makes the play interesting (or relevant to a modern audience).  What makes the play relevant is that it shows how little, relatively speaking, it takes for a good man to be corrupted, for him to turn bad. 

Macbeth is manipulated by both the Weird Sisters and his wife, but once they help him get the ball rolling with the murder of Duncan, Macbeth becomes more and more evil, ruthless, power-hungry and violent all on his own.  He begins the play as a brave and loyal subject to his king, and by the play's end, he has all but destroyed Scotland, his marriage, and himself.  It is this progression that makes the story tragic, and it is likewise what makes the story relevant to any time period.