They want more efficient games. With “efficient” meaning: More fun for less time. Or: If they are shorter and don’t require as much getting into, they should just as much be more intense.
Simplicity vs. Complexity is kind of missing the point, and I think "efficiency" might be a little off the mark too.
My biggest problem with modern games is that the type of complexity that they introduce doesn't make any sense. One way is that they add some sort of "puzzle" or something to solve. But this puzzle isn't solvable by logic or intelligence, it's just something completely random. This is why game walkthroughs are so popular. Some of the predicaments are just so obtuse and weird.
The other way is that they introduce complexity to the controls. This is particularly common in console games, but not unknown in the PC gaming world, either. I want to be immersed in the game, I don't want to spend the time trying to adapt to whatever weird control scheme or combo of button presses the interface requires.
The brain is a wonderful organ; it starts working the moment you get up in the morning, and does not stop until you get to work.