How do you satirize a genre that’s become a spoof of itself?  It isn’t an impossible trick but, to pull it off, it takes a keen eye for detail and a filmmaker who can thread the needle between appreciation and cynicism.  2014’s They Came Together, a comedy from the creators of Wet Hot American Summer that hilariously destroyed the rom-com genre, is the bellwether for me, and this year’s clever seasonal spoof Cup of Cheer…