Well, for starters, I envy you, Will Fly, for your varied experience in music. Then, IMHO
I think there's a place for all sorts of music with the possible exception of hip-hop/gangster-rap. There is a lot of classical influence in heavy-metal. Jazz players generally don't really care what you play or how you play it as long as you eventually get back to the same theme you started with, and the longer it takes, the better. I don't really know how to define "Folk" in the U.S.A. I think that whatever people play and sing on their back porches after dinner and a few drinks is probably American Folk Music. It may be different in West Virginia than in Tennessee or in New Mexico or outside New Orleans, but there are a set of old songs that are native to each area of the country. Some songs will be older than others and some will be fairly new and commercial but in the same general vein as the old ones. I like them all.
It's probably not much different in the U.K. and surrounding countries, they've just been at it longer and they spent more time shooting at each other than we did, so they have more songs with a locally historic perspective reminiescent of the Hatfields and McCoys. So, they take those songs personally. Some of us in the U.S. may share some DNA with people in the U.K. but we don't share their history and can't fully understand their traditions any more than they can understand our lack of lasting deep seeded hostility between the states. A lot of stuff from Nashville gets played in Massachusetts.
I think there's a place for traditionalist music. Classical musicians are taught to play it the way it was written and that's fine, since it leads to good disciplined musicianship. On the other hand, although Segovia transcribed a lot of guitar versions of classical pieces, and his work is generally considered the traditional transcriptions to be taught as transcribed, another classical guitarist, John Williams for example, may embellish the same pieces and it's still considered "Classical Guitar" and not Jazz although he has improvised a little, or a lot, in places.
From what I've seen on Mudcat, there are a wide variety of opinions on individual songs let alone classes of songs, traditional versus commercial, folk versus blues, and that is as it should be. Play and sing 'em the way you feel 'em. Others who share your feelings will think you're pretty good. If they don't share your feelings and you're in the U.S, run! If you're in the U.K. be glad guns are illegal, then run!
The important thing is to keep playing and singing what you like. That's what I want to do.