I agree with you about steering clear of specifics, LH. Thankfully there are plenty of generic themes about the human condition: Love of child/parent/partner/nature, frustration/courage against adversity, fear of unknown/loss, striving to improve one's lot, joblessnes, hunger, war etc.

The relevance of trade-specific songs tends to peter out as the trades themselves disappear, any remaining relevance being symbolic only. Mining or canal songs in the UK are heading that way. Fishing songs retain their relevance, but for an ever-decreasing community.

Perhaps one exception to the above are songs specific to a particular war or battle, recounting the details to "pass on the lessons" as it were. So "Green Fields of France" and "The Band Played Waltzing Matilda" can still feel relevant 100 years after the events described even though the mechanics of war have changed drastically meanwhile. And separation from loved ones still hurts, so "Farewell to Nancy" will always cause eyes to well up. All of which is a way of saying what a great songwriter Eric Bogle is!