It is getting a backlash from gamers who have never played the previous games or maybe just played NV and F3. They also think that the game should look a certain way regardless of how big it is or what the engine is doing in the background.
Everyone else who knows what the game is going to be like already know that visuals take a backseat, and also know that the visuals have been improved and are content with how the game looks.
I posted a video a while back of fallout 3 in the Fallout 4 thread. When you look at that and then look at this, the jump is obvious & huge.