Unlikely that IS should degrade shots. What was your focal length and shutter speed? Also, what were you shooting?
1DX, 5D3, 600D, RX100
16-35L, 24-70L II, 70-200L II, 100-400L, 50L, 85L II, 135L, 24TSE, 40, 100 macro, 18-55 II, 55-250 II, 1.4x III, 2x III, 600RT x 4
The grass is always greener when you crank up the saturation in photoshop