Or maybe Doom 3 is what Doom would have been had it been created a decade later? Who knows how much of Doom is down to technological and time constraints and how much was intentional?
I sincerely doubt that Doom 3 was the vision the developers had while making Doom 1. It still doesn't matter though. Once a series is established with a specific style and type of gameplay, that's what that series is about, whether or not that is what the people behind it intended in the first place. Deviate too much from the established formula in an official sequel, and there will
be a backlash. One which usually could have been avoided simply by changing the title of the game to make it clear that it was not
a part of the established series. Like New World Computing did with Might & Magic and Heroes of Might & Magic. The game might even be loved by fans of the existing series on its own merits, while they would have hated it if it had tried to mask as a true sequel, simply because it was completely different from what they expected.