This single sample does not prove the lens is soft. The more likely issue is testing method, especially focus accuracy.

A handheld AF shot can be affected by many variables besides the lens: slight subject/camera movement, AF missing the intended point, focus-and-recompose error, in-camera JPEG processing, body calibration issues, or even shooting closer than the lens’s minimum focus distance.

To test lens sharpness more reliably:

• use a tripod
• turn IS off on the tripod
• use a well-lit, flat target
• shoot at low ISO
• use RAW if possible
• use live view/manual focus for critical focus
• use mirror lockup or a remote/timer to reduce vibration

This lens is generally regarded as very sharp, even wide open, so a soft-looking handheld sample at 100% is not enough to conclude there is a lens problem. If repeated tripod tests with careful focus still look soft, then investigate autofocus calibration or a lens/body issue.