[solaxun]

Separating concerns the way you describe can be accomplished leveraging the polymorphism mechanisms in an OO language (objects and subclasses) or just as easily in a functional style (multimethods, protocols, interfaces).

Show me an example of something you think is decoupled in OO style which could not be similarly decoupled in FP, and I'll give you the FP version which does the same.

Not saying one is better than the other, but you can definitely keep your code decoupled in both styles.