Alfred Hitchcock said, "A good story is life with the dull parts taken out."
I agree that no scene in a good novel should be "dull", per se...but I have a hard time with what I've been reading lately in advice to writers about adding tension or conflict to every scene.
I've also read that readers need a break in the action or tension to relax for a moment...to breathe. Otherwise you are beating them to death with tension & conflict...and that hurts.
I think the good advice lies somewhere in between. The key is the levels of conflict or tension added to each scene. Some scenes will simply be builders of tension, rising to a heavier conflict in another scene. Others will have huge conflict that throws your characters into a situation, or into the main climax of the story.
The conflict or tension in a particular scene may be physical or emotional...but it will always advance the plot in some way, whether small or large.
A good story needs an ebb & flow of tension & conflict, the same as life gives us...but the dull parts are definitely best left out.
One thing I have been so impressed with since I started writing is the amount of advice that's available to new writers...sometimes for free. But it's also been frustrating that with the abundance of advice out there, a lot of the ideas seem to contradict each other. =P
I'm a newbie still learning as I go, but I've found it most helpful if I use my own sensibilities and understanding of my story to figure out how to use every piece of advice to my benefit. =)