The author did not make it seem like that, they explicitly pointed out otherwise, the 5th paragraph:
> This is not to say that there aren’t some benefits to breastfeeding. In poor countries where water quality is very poor, these benefits may be very large since the alternative is to use formula made with contaminated water. In developed countries — the main focus of the discussion here — this isn’t an issue. Even in developed countries, there are a few health benefits of breastfeeding for children in the first year of life (more on this below).
> Infants in the treatment group — who, remember, were more likely to be breastfed — had fewer gastrointestinal infections (read: less diarrhea) and were less likely to experience eczema and other rashes. However, there were no significant differences in any of the other outcomes considered. These include: respiratory infections, ear infections, croup, wheezing and infant mortality.
Apparently so, did you read the post you are criticizing?
Emily Oyster wrote good books about how a lot of the popular claims around giving birth / raising children have quite a severe lack of data that supports those claims. For breastfeeding in particular there isn't much data to separate whether breastfeeding is actually helpful at all vs being in an economical position that would allow someone to breasfeed.