The simple truth is that breastfeeding does not provide any extra advantages. It's just the biological norm. Children who do not receive the biologically normal diet will suffer certain disadvantages.
Now, I get that this statement threatens people who chose not to breastfeed, and that it hurts people who desperately wanted to nurse but could not. So it's a message we should present carefully. But any deviation from the biological norm presents certain harms.
We don't say that a smoke-free environment makes people healthier; we say that smoking causes disease.
If we wanted to, we could provide (virtually) every child with breastmilk. First, we need to be clear that it's extremely important -- important enough to make maternity leaves much more generous. Important enough to teach expectant parents about breastfeeding in a meaningful way. Important enough that we change our birth routines to support breastfeeding. Secondly, for those who cannot nurse for any reason, we need safe and free milk banks.
Outside a handful of very rare medical conditions (like galactosemia), every single child should be fed breastmilk exclusively for the first six months, and breastmilk should continue on for at least another six months, and that is really not long enough. That is minimal. I nursed my children for 3-plus years. So did my daughter. Kids wean themselves when they are ready. Normalize full-time breastfeeding.
I'm not actually disagreeing with you, and I hope that's clear. I'm just offering a different perspective.