This song completely surprised me. Since you said it was for national day (and since I had never previously heard a Singpore National Day song), I was expecting something much more martial/marching band style. This sounds like Christian music!

This is 100% correct. They say familiarity breeds contempt, but it's not as simple as that. The familiar is comfortable, and we do like to be comfortable. I can't say how many times I've come to like a food or a song simply because of repetition.