You can't ignore it, unless you want to deal with a laughable health/armor/ammo pool und run out of ammo constantly. Also the "secrets" are mandatory, because almost all equipment is served there.
BTW: Secrets were never a signature feature of DooM (1993), but existed in any video game of the era and were entirely optional (usually added after the main campaign was finished and balanced).
There is one reasonably good map (which is what all reviewers played), appearing after the tutorial/demo section, then it turns into the usual linear one-way sequence of arenas. The arena gameplay has nothing to do with the gameplay of the original, nor with the original level design, but a lot with what bad WADs offered.
The later parts of the game, especially the hell section look atrocious. Compare this Doom³ (2004), which started too slow as some kind of Resident Evil , but turned into complete awesomeness once you reached the portal. The real signature feature of the DooM franchise always was the excellent artwork.
I think the Bethesda developers played some mod/total conversion and believed it was the original DooM formula.
