I'm playing it now. It's not that bad. It's the level of humor I expected from a Duke game. I guess some people expected something better than DN3D. Take off the nostalgia glasses and you'll see this game was everything they intended DN3D to be.
I have a hard time believing DN3D was intended to be terrible 
You don't think the same ideas present in DNF wouldn't have found their way into DN3D if it would have been technically possible? You don't think DN3D didn't basically copy the FPS concepts of the time and add "interactivity?" I think you wildly overestimate people like George Broussard.
I'm telling you, a LOT of the hype around DN3D is nostalgia glasses. DNF will never be good, or even passable, to the people comparing it to DN3D regardless of the choices Gearbox/3D Realms made. Am I telling you the game's awesome? Heavens no, it is far from awesome. Am I telling you it is terrible? No, it is not terrible either.
It is an average game, and DN3D was an average game that gets placed on a pedestal because "OMG I REMEMBER THIS FROM WHEN I WAS (insert age here)!!!1 PIXELATED TITIES WERE DA BOMB!!!"