> Liberal western politics are based on individual liberty and free will.

> However, mainstream science maintains that we're neither individuals nor have free will.

You are conflating government control and social interactions. Liberal western politics is based on individual liberty and free will in the context of government policy. Such policies are focused on reducing the control that governments have on individual rights and not how individuals are influenced by other individuals within societies, which is the topic that Homo Deus and Sapiens focus on.