> Maybe a tangent idk, but how do unitary universalist groups work or religious communities without afterlife reward doctrines?

Unitarian-Universalists aren't growing, they are shrinking. Most denominations are shrinking, but on the whole, conservative denominations are shrinking rather more slowly than liberal ones, including the super-liberal UUs. I remember, when I was younger, I tried out a few different churches. I saw more than one conservative Protestant church overflowing with young families. I also went to a Unitarian church (only one, but there aren't many around here), and I was the only person there under 50.

In general, religious communities without afterlife reward doctrines, struggle to survive and thrive in the long-run. Their members tend to defect either to secularism or to religious communities which make bigger promises