If you are able to breast feed, and willing to make the sacrifices necessary to do so: you are a "good parent" in respect to breast feeding. If you know something (like breast feeding) is optimal for your baby's health and development and refuse to provide it--because you place a higher value on your time free of child care or on discretionary income: purchasing power for "non-essentials" like clothes, vacations, more housing than you need, etc,-- then, no, you're not a "good parent" in respect to breast feeding or whatever optimal thing you are withholding from your child.
Formula is only a seeming convenience that emancipates women from a certain amount of infant care. Hired help can do it for you and you don't have to be available when your baby is hungry. "Seeming" because there is no advantage to exposing your child to a higher rate of disease (for example: allergies, infections) or to limiting their intelligence.
For women who absolutely can not/won't physically lactate, breast milk is available from local milk banks.