I wanted the problem to be almost anything except the obvious one. My 3D printer was tuned well enough, my bed was clean, my filament was dry, and my slicer profile looked respectable at a glance. Yet print after print came out with ugly walls, rough top surfaces, and seams that looked more like damage than a normal part of the process. I kept changing everything around the failure instead of admitting that my extrusion settings might be wrong.