Couples who are capable of having children have a moral obligation to have children.
NFP is intended to provide a respite if necessary in a larger context of having children.
For example, my friend who was advised by her doctor after a couple of miscarriages to take an 18-24 month break between pregnancies in order to reduce the chance of further miscarriages.
That is an appropriate context.
Correct. There are frequently cases where, for a serious medical reason, a woman who already has children to care for, may need to avoid another pregnancy for a limited period of time.
That is one value of knowing NFP. On the the other hand, NFP can be helpful when couples want to achieve a pregnancy.