I think that we ought to bear in mind that, when criticising the rhymes in old folk songs, pronunciation, along with spelling, has changed over the centuries. We have all had a good schooling with the modern english language well to the fore in the curriculum. Shakespeare with his plays and sonnets,and the hacks down in Seven Dials churning out broadsides however rhymed according to the then valid pronunciation. For example, wind was, I believe, once written as wynd- as in "O Westron Wynd", and, if classically trained singers are to be believed, pronounced as 'wye+nd'. Furthermore, most traditional songs reflect the dialect/patois/argot, and so the pronunciation, of the region where they were collected, which is why modern RP often grates and leads singers to 'correct' the rhyme.

With 'modern' songs, on the other hand, I have to agree that the rhymes can be strained, even cringeworthy, although this is often more apparent if you read rather than sing the text. I also have to admit that I'm as guilty as the next songwriter when it comes to this. It's like the old jazz song puts it:"It ain't what you do, it's the way that you do it..."