Dave,

I think Roman said what I believe to be "wrong" with your image. Without a stronger foreground element, splitting the image evenly between the foreground and the background creates the blandness that you noticed. The sunset is very dramatic. Why not frame the image in a more classic fashion by having the horizon be at about the bottom 1/3'd of the image and then use one of the taller cacti in the immediate foreground to frame the image? That would give the viewer an immediate focal point up close, then "wander" into the image across the landscape, before settling on the spectacular sunset, ie. the background?