The LCD thing is a technology of itself regards of what you present on the screen. LCD pixel are form of squares (or perhaps hexagon), so you cannot draw a flat line diagonally because there will be jagged like stairs. The more closer you look, the more obivous it gets. That is LCD and nothing to do with camera. Take your painter software or Visio, magnify to 300% and draw a line. Macs add a layer of LCD screen filter to smoothen up the surface so that it is less obvious but the jagged still present.
Assuming every setting is optimal, the blur may be due to optic quality. If one is pondering why some people can take very clear close up insect macro like PTroy, that is bec he photographed the insect in distances of inches not feet.
The higher the zoom used to take the picture, the lesser you can crop.