Songs need to be a byproduct of an experience or stirring in our spirits rather than just a craft that we learn. Our crafting skill can help us put that inspiration into a Palatable form so that congregations can share the same thoughts and expressions that birthed the song. For me it's always inspiration first, and then the craft skills to properly assemble the inspiration. At worship seminars I am frequently asked to critique songs written by those that attend and almost always the greatest mistake people make is that their lyrics don't specifically focus on a main theme. Almost every successful worship song I know has a distinct statement or theme that is constantly repeated which gives it an undeniable identity.
Congregational music demands simple melodies that have character at the same time.
Many worship songs fail the test of time because they're just not singable. Worship songs must be written in such a way as to allow congregations to focus on who they are worshiping rather than complicated twists in a melody line. Great worship songs flow melodically with ease like a river finding the natural path of least resistance as It moves downstream. The melody and musical feel are Majestic and give you the sense of being in the presence of royalty. The melody and musical feel are simply the road that delivers the lyrical expression contained in the song.