Who needs concrete story structure when you have an absolutely captivating cast? With no real Main Character at the center of it all (though there are instances when Nic (Annette Benning) seems to be the one) the film becomes less of an attempt to argue a specific point-of-view and more of an emotional experience. More slice-of-life than problem-solving. The film moves effortlessly from one emotion to the next, granting audiences a rare, yet welcome, glimpse at the world from a more holistic perspective.
Usually, a complete story is required to generate the impulse to experience a story again and again. The Kids Are All Right would be the exception to the rule.