I'm largely in agreement with you, but I would argue that "folk", at the very least when it's applied to non-field-recorded artists, has always been nebulous.

Chartex, perhaps you would like to come up with a meaningful, substantial definition of "folk". You may find that the term communicates less than you think it does. "alt-folk" is still nebulous, but I think the term is understood better by those who use it than "folk" is.