Don makes a number of very valid points about good melodies but you can follow the principles he sets out yet still keep your melody within a fairly limited range. Maybe a little more than the fifth or sixth he mentions but certainly within an octave or maybe a little more which keeps the melody within a range that most people can sing.

I suspect that some of the problem with the singer-songwriters that Don so roundly condemns is that for them, the words is all that really matters, so they give little thought to the melody. Many are really aspiring poets at heart, but presenting their efforts as songs means they have a potentially larger audience and they do not realise that for the poem to become effective as a song they need to put as much effort into the melody as to the words. In fact, it is possible to take an indifferent poem and raise it to another level by marrying it to an effective melody which also is sympathetic to the rhythm of the words.