The whole point is the WAY songs are done.If a really good song is done too slowly(or too fast) by the wrong singer, it can effectively
kill the song. And the Irish Song thing can be laid firmly at the door of those publishers of books that state 'The Irish Song Book' and then include songs written by Australians Scots and Americans.
AND of course where the song is performed.A Folk Club or Concert
Audience might not be impressed by your Wild Rover, but do it as part of an 'Entertainment' evening and the audience will be stomping along in time.
Innaccuracies and factual errors are what stops me doing some songs The Witches being an example, when the number of women killed by the Inquisition is usually greater than the population of Europe at the time of the Inquisition. And The Alamo -- Young Davy Crockett was about sixty wasnt he ?? Gawd I could rant on for ever but I must go and rehearse American Pie for my next Medieval Banquet.