I’m actually of two minds of this. If a word is part of most people’s experience, you don’t have to explain it. What child doesn’t know what a blog is, or voicemail? But if Britain is truly multi-culti and post-Christian, then the church words become even more important, because they aren’t part of everyday experience for many youth, and they are such a part of the literary heritage. Is “fortnight” in there? (Made famous by Robinson Crusoe…and as a child I never understood what a “Popish prayer book” was…maybe “pop-ish”, like a missalette.)
As for the “country words”, plants and animals are hard to define. You can figure out by context that a buttercup is a flower, but if you’ve never seen one, it’s hard to get the picture. It’s a lack of nature literacy we’re discussing here, not one of words. Likewise, with all due respect to Breda’s sacred food, you know bacon, or you don’t. Is “fetayer” in there, or “kibbeh”? Just checking.
In short, this is more a symptom than a cause of Britain going downhill.