Whether or not I put depth in the things I make is exclusive to the aspect of the actual art side of the work.
Sometimes it needs it.
Sometimes it looks better without it.
My artistic ventures extend far beyond signature making, but forums do it minimal justice.
Blurring + sharpening is not "depth". It's a start, but hardly a principle.
Depth involves perspective, a vanishing point (if not more than one, depending on the piece), choice of coloring, shading, dodging, sizing ratios, etc.