Ah, that's an interesting angle. If I understand, you're saying that we have an innate need to be in a tribe, and these religions fulfill this need? If so, then we just need to increase the secular humanist marketing budget, and offer folks a more sustainable, inclusive, and healthy tribe to be a part of!
Because Humanism is by definition individualistic. That's not what people want. Have you noticed that, in Christianity's collapsing state in the West, people are turning to Islam, not Humanism? The number of Jews becoming Haredi has skyrocketed.
People want to be told do this, do that. It's what life was like with our parents - when we were safe. We didn't need to choose how, what to eat, wear, watch, read or do. It was chosen for us. It's this kind of security people crave. There's only so much freedom a human can take until the responsibility and loneliness become too much.
In fact, now I recall, it's one of the four primary causes of an existential crisis:
"To be free means to be responsible for one’s life, the author of one’s own destiny. Because of the overwhelming seriousness and importance of this task, people frequently flee from freedom and hence the responsibility of determining one’s own path in life.
To the extent that one accepts their freedom, and thus the fact that one is responsible for one’s destiny, one is faced with the chilling realization that one is alone. Existential isolation, referring 'to an unbridgeable gulf between oneself and any other being', is another ultimate concern that each individual must come to terms with through the course of their psychological development."
