Before you can determine what a "modern folkie" is, you first need to decide what a "folkie" is. And you also need to decide what you mean by "modern."

Is someone currently living (a "modern" person) who sings very old traditional songs and ballads and accompanies him/herself with a lute a "modern folkie?"

Or is a "modern folkie" someone who only sings modern songs. If so, how modern? Or, for that matter, does it have to be only American folk music? What if they sing Irish songs? How about Balkan music? Brazilian? Swahili?