In my opinion a macro is all about the resolution of detail.
A well done macro picture needs to reveal details one could otherwise hardly appreciate with the naked eye.
This is up to lens / sensor / film and of course skill of the photographer to focus correctly and eliminate motion blur.

To review the marco, the display medium (screen / paper print) should be capable to display the necessary amount of graphic image data from the original file or film in order for the viewer to observe the enhanced detail not visible throught normal observation.

The display / paper should be large enough and have enough resolution to reveal all graphic data at once or in case of screen display it can be achieved by zooming in on parts of interest to confirm marco nature of the image.


In theory a mini display with an insane pixel density could still display the macro photo with all enhanced details inherent to a macro but for the observer it would be pointless unless he was going to zoom in partially and / or use a magnifying glass over the mini displsay to confirm this is in fact a macro image.

To only blow things up larger than life but out of focus does not qualify for a macro if looking at the original with the naked eye still reveals more details.

Below cropped shot with a Samsung Galaxy S7 Edge blows up the subject well enough but hardly reveals more detail compared to real life so with my current level of eyesight I personally would call this an average macro picture and camera.