Of course nobody knows what any skill really does.

I think of creativity as the ability to make "Less than obvious plays". Imagine that using attacking, mixed, mixed means players usually pass straight up field to the player highest up on the same side of the field. A more creative player might be more likely to move out of position to make a different choice, or to spot a player further away with more space and time available. Defensively, low creativity might lead def players or GK to try direct long pass to a crowded ST rather than finding the smarter options and working up.

I think of it like "field of vision", more creativity= more options.