I think it's more likely that we wouldn't have thought something like Doom to be possible until Carmack came along and squeezed oodles of math tricks and hacks

I think it's more likely that we wouldn't have thought something like Doom to be possible until Carmack came along and squeezed oodles of math tricks and hacks into the game to let it run on hardware of the era. So it may as well have be an infinitely long development time for us.