While I don't consider myself a musical snob, there are genres that I enjoy listening to and playing more than others.
The way a melody is harmonised can depend on the person playing the song. When I was learning to play guitar circa 1960, I had just learned a song called Jack O' Diamonds from a Burl Ives songbook. It suited me at the time, because I could play it with two of the three chords that I knew.
(G) Jack O' Diamonds, Jack O' Diamonds,
I've known you of (D7) old, Boys, I've known you of (G) old.
You robbed my pockets, robbed my pockets
Of silver and (D7) gold, Boys, of silver and (G) gold.
One day I went to a coffee house in Hamilton, Ontario to see a fellow named Jackie Washington. He played my song, but he used two chords for every measure. I ran down to Waddington's School Of Music the next day and bought Mickey Baker's yellow and black jazz guitar book and Jackie Washington became my guitar hero.
Jack O' (G) Diamonds, (GMa7) (G6) (GMa7) Jack O' (G) Diamonds, (Am7)(A#m7)(Bm7)
I've known (Bbm7) you of (Am7) old, (Am6) Boys, (Am7) I've (D13b5) known you of (G) old (Bm7)(Bbm7)(Am7)
James Taylor took a simple folk song, Oh Suzannah, and played a simple Travis style 3 chord instrumental version, but when he started singing, he made some more complex chord substitutions. I'm not sure if these are his, but they're a close approximation:
I (A) come from (Bm7) Ala(C#m7)bama (F#m7) with a (A) banjo (F#m7) on my (Bm7) knee (E7)
I'm (A) goin' to (Bm7) Louisi(C#m7)ana (F#m7) My (C#m7) true (Cm7) love (Bm7) for (Bb) to (A)(Ab)(A)
(D) Oh Su(Bm7)zannah(E7) (A) Don't you (F#m7) cry for (Bm7) me (E7)
I (A) come from (Bm7) Ala(C#m7)bama (F#m7) with a (C#m7) ban(Cm7)jo (Bm7) on (Bb)my (A) knee.
You can "jazz up" almost any simple song by substituting more complex chords. Whether it's wise to do it or if it improves or even ruins the song is a matter of taste. I like to keep some songs simple, but sometimes it's fun to make them a little more "swingy".
I recall playing Hey, Good Lookin' using chord substitutions and giving it a Western swing feel and when I'd finished, a Hank lovin' friend, Lance, said, "Jim, of all the tunes to F#$% up with a bunch of jazz chords, why a Hank Williams tune?"