But I think the idea that revival & post-revival singers are keeping traditional song alive, or that the tradition is still being added to, is a bit of a mirage.

Then what you need is an optimistic over-dose of Steamfolk to disavow you of such a potentially dispiriting notion, especially if you're singing from the Kipling/Bellamy Songbook which stands as vivid testimony to the purely Idiomatic vibracy of the thing. For healing therapy and communion with angels, try singing Bellamy's setting of The Anchor Song as loud & fast as you can and your soul shall be cleansed! Get it right, then do it in front of an audience and they'll be buying you pints all night.