I mean, at least a baby should be breastfed (as in a balance between formula and breastmilk) while there are those who solely use formula as their main means of feeding the baby but later in life that child has issues with their immunity like being susceptible on illnesses that are typically not fatal for most people.
That’s because breastmilk has all the nutrients to strengthen immunity later in life for a child. There is a difference between breastmilk and powdered milk: since formula is composed of numerous chemicals (it’s made from compounds) while breastmilk is from the mother. Is breastmilk healthier than formula?
Formula is a lot better than it was a few decades ago. While breast is best for a variety of reasons (immunity support and bonding foremost) if for any reason you can’t, formula is perfectly fine, even if it’s only formula, and there’s not going to be any long-term problems because of it.