I recently ran across what I suppose is a fairly common attitude.
Why do people insist that a picture should have meaning? Why must it evoke emotion? Why can't it just be a good picture?!!!!
The sticky bit here arrives when you try to get a handle on "just be a good picture." Looking closely at what a good picture might be, where by "closely" I mean anything but the most superficial examination, you find that a good picture has to make some sort of connection with the viewer. With many viewers, in fact.
You could argue, I suppose, that a picture can be good if it's sharp, if the composition meets certain geometrical demands, if the colors are sufficiently vibrant. This would be a frankly bizarre argument, but I suspect that it is the road many would start down in trying to rebut me. You might start down it, but would quickly realize that it's a a dead end. Technical merits in the absence of emotional connection do not a "good picture" make, there's simply no denying it.
If a picture makes a connection with a viewer, it's evoking a feeling or telling a story, or something. Something is happening inside the viewer's mind. That's the point. That's a minimum criterion for a good picture.
That's why it's not enough just to be a good picture -- there's no such thing as just a good picture, without message, meaning, emotional connection of some kind.