The community you descibed, seems something good - that I would not just write off. A lot of Atheists attend UU churches. Just saying.
In my case, leaving after having been a JW most of our lives, lead to loosing every last friend. There are no UU churches where we live and as an Atheist I do not want to expose the children to religion. In the five years we are out, we have slowly and gradually built a small circle of friends - from work, parents of our childrens friends, in the neighborhood, etc... But remains indeed an area in shich we somewhat struggle. We do some volunteer work and also find some satisfaction in that, with like-minded persons.
No silver bullet here - but true unconditional friendships take time.