I think the infantilization was to permit a large brain through a small birth canal. The trick is to have a long infancy during which most of the brain growth occurs.
It will take more than this to show that Neanderthals were our ancestors.
The small face and jaw are also a feature of human infants. From what I have seen of Neanderthal infants, it was also true of them. Females normally have such features and if somehow these can be fixed in the males we have something approximating homo sapiens. IAC, I am bothered by so much specuation based on skimpy evidence. Extrapolations from present data, in either direction, is chancey, especially if it is driven by a philosphical agenda.
Where do Cro-Magnons fit into this equation?