Well I have to say a few things about this, since Doom2 is my all time favorite FPS of all time. First of all from the article, this was after the first reboot of Doom4:
At one point, a source told me, the Doom 4 team had a big meeting in which company leaders talked about what Doom meant to them. John Carmack got up in front of everyone and said something like, "Doom means two things: demons and shotguns."
Why didnt they just stick to this? Well two things IMO. Rage. Zenimax. Thats it. id is not the dev house it used to be, it ceased to be anything other than a subsidiary the moment they sold out. Just like every single other well established dev. Its the crappy reality that most fanbois dont want to face but thats it. iD in name only.