As the ridiculous Shakespeare whodunit movie, “Anonymous,’’ slips beneath the waves, you have to ask yourself: Whose idea was this? Not only is the tangled question of who “really’’ wrote Shakespeare’s plays (Edward de Vere? Francis Bacon? Kit Marlowe? There is endless material for sequels here.) absurdly arcane, there is one yawning fact that the producers of “Anonymous’’ overlooked:
No one cares.