The concept of folk exists. It is differentiated from other musics. A valid question here is not the definition but who gets to define it.

An even bigger question is who today cares? A comparatively small group.

I've tried to discover what it is by singing it myself and listening to others who I felt were part of a tradition. I never claimed to be a part of any tradition of any folk song except when my step-father taught me a blues song he had heard hobo-ing around in the 30's.

The reason I think that it exists is that it contains a kind of aesthetic. 1. It's generally accessible. 2. It has parameters. Not a wide vocal range. Basic language endemic to the culture. 3. Singing style is not classical or trained. 4. It has been passed down.
5. Content is usually narrative. 6. Much of it requires footnotes to understand its background. 7. Harmonic content is simple. 8. It is not adorned with the standard show business physicality of rock or pop or even some classical. 9. It sounds best in a smaller more intimate environment, not on a big stage. 10. People who are part of the culture which spawn the style recognize it as their own. 11. It is associated with working class culture.

There is a folk-like performance style that is sometimes appealing and sometimes contrived in its imitative approach.

I don't think that it can be duplicated by those outside the culture with much success.
There is a genetic as well as cultural component.

What we see in today's performance style that is reputed to be "folk" is more of a show business image thing.

I see it as separate from other forms of musical expression.

Frank Hamilton