You can’t create secular alternatives to religious organizations, it’s like creating an alternative to a bar with no alcohol. You get something vastly more different than that would suggest. Churches and other religious organizations are based on a belief in something higher or transcendent that is lacking in secular organizations. All attempts to provide them have been miserable failures. Sunday Assembly was the last major attempt in the US, failed, humanist associations have a long history of being for comically tiny minorities compared to even extremely marginal religious communities. Communities require people to show up, regularly, whether they feel like it or not, with family.

There was a wonderful article I read ages ago and can no longer find on the history of communes in the US over the 20th century. Not one secular commune managed to perpetuate itself across generations without turning into something vastly less communal. Most religious communes failed too but the Amish and Hutterites are practically ethnic groups based on religion and there are lots of smaller groups.