No wonder this work is posthumous: Winnicott never could define human nature only with the psychoanalytic framework; he needed the historical, economical, political and sociological sciences to postulate something more concrete.
Instead of an interesting investigation we have a jungian and biological approach that divides human spirit in male and female with some elements repeating on the basis of soma.
While his research on children pathologies is outstanding, this books doesn’t develops his previous theories much further.
What we have here is an ideological view of how human is static and only reacts to environmental phenomena (something pretty tautological if you ask me).
Human nature as such doesn’t exist, what we have in each epoch is a manifestation of the human spirit thanks to the spirit of the mode of production that is ruling. And that isn’t a deterministic point view, let’s remember that Thomas Müntzer opposed the spirit of feudalism through revolutionary actions, doesn’t that tells us more about human “nature” than the soma?
The same goes with Marx, Lenin, Stalin, etc.
They could pinpoint the symptoms, the illness of the human spirit in the capitalist mode of production to rebel against them. Winnicott, Lacan, Freud, etc. do the same but forgetting (or doing so deliberately) the full social panorama, and end up reproducing the ideology that gnaws us.
If we want to speak of a human nature, then we have to by materialistic and dialectical means, or in other words, considering the full socioeconomic relations that dictate each historical moment.