This denial means we can feel more at ease when our hyper-productive lives force us to ignore our children's need for our presence. Kagan wages a systematic assault on the idea that infancy is developmentally important. Terms like these are vague and simplistic, and can easily be used as an excuse for abuse and neglect unless some definition is given to their meaning. As a rule of thumb, yes, children can be resilient. They can usually recover from isolated or unintended hurts.
Resiliency fails in the face of repeated, ongoing lack of attention.
When something painful keeps happening to an infant, such as not being picked up when they cry, this does have long term implications. In other words, to the extent that the policy is to respond warmly to infants' emotional needs, to provide ample eye contact and physical nurturing, to allow dependency as well as support their seedling attempts at autonomy at their own pace, then resiliency is fostered and mishaps won't have lasting effects. There is something obscenely reductionistic about categorising people into 'fine' and 'not fine'. Yes, most adoptees go on to lead creative and fulfilling lives. But their richness and uniqueness as individuals includes a host of often difficult, usually profound, and sometimes painful, inner experiences that many of them need to come to terms with, such as feelings of grief and confusion.