The fun thing with DNF is that most sites went on saying that it was a 90's FPS that felt dated, blah blah. I found the true problem with DNF to be that it was basically Halo with Duke-themed stuff. The things that hamper DNF are the same ones hampering Halo:
- Linear level design, can't really explore everything: Check
- Carry only two weapons: Check
- Regen health that gets you killed quickly while waiting for refill: Check
I'd add the long loading times, and the surprisingly LESS interaction with the environment compared even to older games like Doom3. Hopefully they'll fix this on a sequel.
Interesting tidbit: my 15 year-old stepson (who was porn after Duke3d came out!) actually liked DNF, sans the loading times. Maybe it isn't that much dated?