Shakespeare's plays, in particular his tragedies, have plots and characters that have become archetypes both in the sense that they are typical examples but (often because the earlier works have been forgotten) they are held up as originals of the type of plot.
These stories often have examples of tensions within families.
Romeo and Juliet. Son and Daughter of warring families fall in love (against the will of these families) and meet a tragic end.
Hamlet. Son finds out his father the King was killed by his uncle who marries his mother. Goes mad (or pretends to) as he seeks to exact revenge.
Macbeth. General, encouraged by his ambitious wife, kills his King to take power. Things don't work out.
So the commentators here are just saying that the story of Creed and Drago when said out loud almost sounds like the summary of a Shakespearean tragedy.