Classical and contemporary art have different criteria.

The criteria can be spelled out for different competitions, but still subjective, not objective, based on judges' interpretation of criteria.

You may want to look up the official definition of subjective and objective.

Criteria can vary as well based on the purpose of the competition, and perhaps many other reasons. 

And don't forget the audience, which is one of the factors factors affecting in-practice criteria.

The bottom line is --- Art is subjective, not objective.