The word Traditional come from the Latin Trans (across) and Do (to give) so it literally mean a song that is handed down (end of lesson). A song that might not seem 'traditional' to a judge in a competition (who may be a contemporary of the composer) could well be traditional to a 16 years old (possibly handed down through at least 2 generations).

What your up against here is the adjudicator's predjudices, and often its impossible to know what they are until they give the results. Best thing is to keep singing songs you like singing. If traditional is defined in the rules, go by that definition. Don't worry too much about the competitions - music was never meant to be competitive anyway - Although its alway nice to win something.