Exactly Klaus, it's so blatant, and it's so clear that an enjoyable experience could lie beyond the game up to that point without that sudden change of tone.
Even the existing game, just as it is, would arguably be better if you deleted all the enemies and Booker walked empty streets, and never had to kill a single person (or perhaps only one or two key antagonists, I'm sure you can join the dots).
Take the energy expended on the combat system and all the various adversary types and put it into the general setting (which is already quite rich, eg the incidental dialogue, the little cinema stations, voxaphones etc) and you've got something special.
