“Mom’s not the same person she once was,” narrates adolescent Noah Bloom (Griffin Murray-Johnston) over the coda of “Penguin Bloom.” He continues, “She’s not the person she wanted to be, but for me, she’s so much more than that.” This is ultimately the place at which any movie centered around the experience of living with a disability should arrive, acknowledging that the paralyzing fall endured by Sam Bloom (Naomi Watts) does not mark the end of life as she knew it but rather a reconstitution of it. If only what led up to this moment in the film made Noah at all a credible standard-bearer for such a message.