I have struggled for years to find a replacement philosophy of life for Christianity.
Christianity has had 2,000 years of evolution, adaption, and development. So it is a complete worldview and way of life. But it is wrong about the nature of reality.
Any other ancient religion is going to have similar problems. Even Buddhism, Daoism, and Stoicism have these problems.
Humanism, which follows science and reason, is right about reality as far as we know it. But it is not yet a complete philosophy of life. It is strong on epistemology, strong on metaphysics, moderately on ethics, but lacking in human flourishing.
This is mainly because only recently has psychology began studying this area with an evidence-based methodology. There is much work that still needs to be done. We are decades away from developing a comprehensive view of human flourishing.
So what’s a person supposed to do in the meantime? My path is to identify as a Humanist, but add Buddhist, Daoist, and Stoic nights to my philosophy of life. I call this Bodhidaoism, but I prefer the label secular Humanist.