"Technically correct" usually means the photo avoids obvious technical flaws, even if that says nothing about how artistic or interesting it is.

Common signs of technical correctness are:

• correct exposure: important shadows and highlights retain detail without severe clipping
• correct focus: the intended subject is actually in focus
• sufficient sharpness: no unwanted blur from camera shake or subject motion
• natural color and white balance: no unwanted color cast unless intentional
• controlled noise/grain: not distracting or overwhelming
• clean image quality: no obvious sensor dust, scratches, compression artifacts, banding, or heavy sharpening halos
• restrained processing: editing doesn’t look obviously overdone unless that is the creative intent

So the basic test is: does the image render the scene cleanly and accurately according to the photographer’s intent? A photo can be technically correct and still be boring, and a great photo can intentionally break some of these rules for creative effect. Technical quality is the foundation; artistic vision is something different.