Folk songs (for me) are:
singable by untrained, but practiced singers with ordinary vocal ranges easily learnable by ear NOT reliant on expert instrumental accompaniment welcoming of attention but NOT demanding attention sound most satisfying in the evening by a fire or in a candlelit room
All that stuff about generations and a hundred years -- phoey! Gilbert and Sullivan is not folk, though our families have handed it down to us. Church music is not folk, though most is learned young, by ear. OTOH, many country music songs ARE folk music...if you strip away all those steel guitars, overbearing drums, or occasionally unnatural vocal affectations. Of course, if their subject matter is banal or badly expressed, they're still BAD folksongs and will quickly be forgotten.
Yes, there is such a thing as a BAD folksong. Most folksongs are bad and are quickly forgotten.
As for dismay that Phil Staines deserves more respect than John Gorka -- I just don't understand why it matters. Let's face it -- concerts are NOT the ideal venue for many traditional songs. Heck, I think of concert going as more of a social thing than a musical thing. When I saw Makem and Clancy, it was to see *them*, not to hear their music. I can hear their music anytime. At home, I can sing along if the mood strikes me, or more often, I can leave them off, pull out my guitar and sing a few of the songs I've learned from them.