Chord changes can be important of course. Although if you are playing chord to chord, then something else springs to mind.
More and more people in "singarounds" with their folders full of printouts of websites claiming The Dubliners wrote every MacColl song... All in three chords.
Dick mentions above how he did a song recently. I put it to him that yes, he's a seasoned experienced pro who can sing. (Daft as a brush with it mind, but there you go.) Sadly, the dumbing down of what used to be folk clubs is accelerated by people believing the tosh about three chords. Interesting how in order to pull off that lazy stunt the websites claim is easy, you need to be a good powerful singer to compensate.
If you are such a person and wish to use a guitar, do yourself a favour and find the intermediate chords or runs. Your voice requires it. If you can't, try learning more chords anyway. Your singing will improve, I promise.
Back on topic. My fiddle playing "partner" years ago refused to talk to me for a couple of days once when we were doing a stage gig and my foldback failed. I was in Eb and he was in Dmaj. He could hear the ensuing "new age" accompaniment but I was oblivious.