Sigh.

It's a matter of definition, nothing else.
A newly composed song is not a folk song. Yet. It might, eventually, become one if it is rooted in a tradition.
A "traditional" song is, per se, one without known author.
A "traditional" singer is an entity now very thin on the ground, only to be found as source singers or song carriers in this day and age really within the traveller or gypsy communities.
A "revival" singer is a singer of folk songs.

Any sort of song may be good or bad.
Quite simple, really.