Leonard Cohen’s mournful paean to music, “Hallelujah,” has been around for more than two decades now, but filmmakers and TV producers just can’t seem to get enough of it. Chris Hewitt loves the song, but wouldn’t mind never hearing it again as an all-purpose backdrop to some melodramatic plot twist that could have stood on its own. “Great as it is, the song has become the musical equivalent of a tube of toothpaste. Each time it’s used, it becomes a little emptier, a little less effective.”