Actually, crossing that line is precisely one of the most tried and true recipes for successful parody. I think that John Wick, intentionally or not, walks this very fine line so well that it effectively becomes two different movies depending on who's watching it. One is a straight forward, if stylized, shoot em up, and the other is stylized parody. It's not Scary Movie parody, it's just little nudges and winks to the person watching the parody screen.