There's this masterclass on movie scoring:
http://mikeverta.com/product/online-masterclass-scoring-1/
And it's fantastic. It compares Star Wars and Batman Begins soundtracks. Two greatest examples of classic/old-school/golden era movie scoring and modern movie scoring... And it's actually devastating to watch.

Mike (great guy, I took 17 of his classes already and they are pure gold) presents here how motives develop throughout the movies.
In Star Wars the main theme literally follows what's on the screen and what happens to the characters. The same theme is differently orchestrated, harmonized, modulated, with different rhytmic background and counterpoint melodies, it perfectly shows what Luke's experiencing in the given moment, sadness and loneliness on Tatooine, determination and focus when he does some heroic stuff, mystical moments when Obi Wan's voice speaks to him, it has militaristic qualities when he fights in the X-Wing against Tie Figthers, etc. Just one theme, one of many in that film. And the theme alone tells the story.
In Batman Begins. The Batman's theme is literally the same throughout the whole movie. Maybe some slight differences in tempo here and here, but it is exactly same whatever happens to Bruce. He's a thug on the streets, he climbs a mountain, he changes his life, finds a new purpose and becomes Batman, he creates his iconic suit and equipment, he fights bad guys, he saves the city, he's rebuilding the manor... music's all the same. It does not tell the story, there's no character arc in the score, it's just cool music.
Wiliiams' score is the film in the musical form. It's a story reproduced in a sound. It has dramatic structure. Not to mention the themes alone are stellar.
Zimmer's score is great rocking orchestra concert album put next to the picture. Everything's cool about it, it suits the individual moments really well, except, there's crucial difference in the structure compared to Williams' scoring, it does not tell one continuous story.
But today, there's no locked picture, which is really bad for composers who want to do this kind of dramatic scoring. And most importantly, how many can do that? Williams, Goldsmith, Shore, Horner, Herrmann, Korngold, Steiner, Courage, those guys studied symphonic, long-form development, and even decades before they started to score pictures! Now? I'm not so sure...
So, it's "tied to the story vs modular". You cannot take Luke's theme, the same melody, but from binary sunset and put that to the ending ceremony scene, because, even thought it's the same theme, it's so dramatically different, because it serves different dramatic moment. But you can take Batman theme from beginning, middle or end of the film and put it elsewhere no problem, because it does not develop.