Herd immunity sure as hell does reduce transmission. And you won't get that without vaccinating children.
Personal opinion the semi hysterical hand wringing over the imminent vaccination of children is because the anti-vaxers know that's the last shoe to drop.
Card carrying anti-vaxxers are generally not just trying to be contrarian, from their perspective they are genuinely concerned for their and their children's health, however misguided you believe they are. So the hysteria is their actual fear of harm.
How come stuff always gets reduced to categorical descriptions?
Like "prevent" is a pretty high bar, but things are still a lot better if you cut transmission by 50%.