I know what you mean about lacking content and replayability. The game is honestly nowhere near being worth its asking price, especially since co-op still does not work. I think this actually solves the "why wasn't this released on Steam?" mystery. Many people would outright refund such an empty game. It's more of a tech demonstration than anything else and it costs more than KF2/KF1, both of which are fully fledged games with hundreds of hours of replayability AND working multiplayer.
If you can wait until it goes down to $10 then it might be worth it but if you want KF, just go play the real ones.