how do you figure that? couldn't handle complex scripts or big areas or something?
DX 1 looks dated for a 2000 game (even Half-Life looked better, though it had smaller maps), and the enemies' AI is awful.
The problem back then was that Epic games didn't support Unreal Tech for consoles officially. UE 2 was a PC engine only, so they had to heavily modify it to also run on the Xbox. They told the programmer to implement dynamical shadows, but instead, he rewrote the entire engine and then left the company, leaving the designers with a botched engine.
Harvey Smith was also the lead designer on DX1, and generally speaking, I think he's a smart guy and favors "immersive First-person expieriences" over Doom clones.
He's currently the head at Arkane Studios Austin and working on something cool. I can't wait.