The “breast is best” narrative is partly an outgrowth of the Nestle boycott. In developed nations, the difference between breastfeeding and formula feeding is pretty minimal. Minor immune benefits for breastfeeding. Minor weight benefits for formula feeding (formula fed babies gain weight more rapidly as nutrition is always available). However, in developing nations, (powdered) formula is far less safe due to lack of sanitation and formula producers have gotten a lot of justified criticism over their marketing campaigns in developing nations.
In an ideal case, breastfeeding seems strictly superior in terms of the baby’s health even in developed nations. The benefits of breastfeeding vs sanitary formula are small but seem to exist. However, the ideal case is often not the actual situation.
My problem with the lactation advocacy is that many advocates ignore actual difficulties with breastfeeding. Low/insufficient milk supply, pain during feeding, inability to share the burden with a partner, sleep impact, isolation (for women uncomfortable with public breastfeeding or living in places where this is frowned on), career impact, etc. It’s often presented as if any issues are failings of the mother. “Pain? You’re definitely doing it wrong. Supply issues? Just keep breastfeeding exclusively and your underweight baby will be fine. The fact that your baby is in the 1st percentile for weight at 3 months and always hungry doesn’t mean you need to supplement.” Etc.