and people taking responsibility for their deeds and words. Religion allows you to behave either because of fear of Hell/anticipation of Heaven or because you want to feel godly.

Secular religion offers you choices, and no guaranties.

That's why it won't sell.

And there are many secular structures that thwart free will, independent and critical thinking, in elevating something above the individual in order to give individuals' lives meaning and purpose and turning around to require group and personal obedience to that purpose. They have rituals and rites, doctrines and teaching, as to what that pure and true something is, and why it requires compliance, obedience, sacrifice, and why even sacrificing your live for it is ennobling. They have those who interpret the secular creed and preach it, and those who, like the inquisitor or tithesmen enforce the doctrine. They promise secular salvation, not for the soul, but for the body or the body politic.

They have true believers, who signal their piety by acts of public virtue, and those who show their piety by uncovering the sinner and his wrongdoing--now reporting on it to the ministers, now to the body at large. They have the strict adherents, who want the doctrine enforced strictly and with little tolerance, to achieve perfection, and those who are laxer and leave it to the individual (often, but only "often," because they doubt or aren't that strictly faithful themselves).

Like religions, sometimes they're tightly structured, with identifiable organizations and hierarchies. Like religions, sometimes they're loosely structured, perhaps ecumenical in that they reach across organizational boundaries to find common cause on some topics.

If you say that their goals and motives are dictated by a deity, you make that one change, suddenly some look like Christian Reconstructionist movements recast, or political Islam with different goals--theocracies, in a sense. Others look like the WCTU or the Abolitionists did, working for some social change to be imposed on society to bring it in line with true morality. Some allow an easy route for repentance and restoration--you confess your sins, you do penance. Others, not so much, but it often depends on the sin. Even the Catholic inquisition had a means for dissidents and rebels to repent and be restored to the faith--sometimes the penalty was severe, at other times it was trivial. Depends on the sin, or crime, or degree of offensiveness. Depends on whether they're fighting widespread heresy, or realize that they're suddenly in a dominant position can be truly oppressive instead of having to rely on mutual tolerance for survival. Xianity and Islam have cycles like this--as they increase in popularity, they are tolerant and humble--"don't judge". Give them a majority, and they slam on the hobbles and yokes to disempower the non-believers and are all about righteousness. Let them feel like they're secure in power, and things are run laxly; but if they suddenly think there are conspiracies afoot, then they need their purges.

Replace "fear of hell" with what most religions really punish the unfaithful with--political and social exclusion, and loss of position, status, and even employment--and it's easier. You don't want the unfaithful dealing with kids, with the vulnerable, after all. Hell is a late addition to Xianity, and really isn't in Islam or many other faiths. Replace "feel godly" with "feel righteous" or "be honored by others". Now look for any movement that has a higher (secular) goal, adherent-enforcers; look for those who feel virtuous and righteous for their positions, and who feel superior when they punish somebody who falls short of their moral teaching, and who even want to disfellowship those miscreants from society and who do so with zeal.

It sells, really well, because people want to belong to some movement, have people telling them how righteous they are, and want to feel righteous or at least self-righteous. It sells, because it lets them belong to something larger than themselves, and to justify the sacrifice they make and are forced to make. It gives them a common "roof" for relative strangers, and a way to quickly have standing among new groups of fellow believers. "I'm from this congregation, I was baptized 18 years ago and served as deacon" gets you somewhere in any denomination (that has baptism and deacons)". "I was an organizer for this group and served on this committee for 3 years" does the same. Or, "I helped with fundraising for my church/organization, and raised $8,000!" It's good if it's a church building fund, a foodbank run by a church, a Mormon mission, or a liberal cause or political campaign or homeless shelter.

The problem is that having bestowed upon the brow of "religion" all sorts of ignominy, haven't said how horrible it is and how restrictive, it's damned hard to admit that there are structures that most of us are in that serve all the functions of a religion but allow others to dictate beliefs and justifications without a deity's authority. We don't see being inside those structures as those do, and assume that they must be really, really restrictive--and surely we'd never be in anything so restrictive. But just as Xians are perfectly sure that they understand and agree with their doctrines (until they defect), so nobody's compelling them to think the as they do (which is, from their perspective, free and critical thinking), so also you don't disagree with adherents of these secular religions without jeopardizing your standing--and running into some pretty strong headwinds if you challenge conformity. You reason your way to agreement, as in any church, and it's easier if the teachings are inculcated in your youth--you don't see the counter arguments until you already know the correct critical approach to say that they are false ... And if you can't falsify them yourself, well, you know others can. Apologetics, in other words, serves its purpose; the most effective indoctrination happens at home, then among friends and in organized groups with instructors.

You don't have to look at things like the USSR, with its rites and rituals, confessionals, inquisitors, doctrines and schisms and doctrinal changes; with its politruk-priests making sure that doctrinal purity was maintained in military units and who were responsible for the moral upbringing of kids in schools and purity of workers and its catechism. With saints' tales from to serve as models of virtue--from tales of young Lenin to the fictional Pavlik Moroz to the stories by Arkady Gaidar featuring Timur.

Masons serve the same role for some. There are no shortage of conservative analogs, some with vaguely religious trappings but secular in everything but name. And there are organizations and structures, some loose and some not so loose, on the left. Look around at various moral movements in political clothing. Most of them have trappings which, if you put a deity in them, make them look a lot like liberation theology. One thing they all have in common, from the USSR to the Nazi millennium to current Western secular religions is that they all offer a path to human perfection and to create a perfect society, an end to history just as Christian eschatology has an end, when humans are perfect and live in peace with each other. They espouse a version of morality to achieve that end, and ultimately they acquire enforcement mechanisms--but they always drip with self-righteousness and often with hypocrisy.

The problem is as soon as you relax the strict and to some extent inaccurate definition of what a religious organization is like, suddenly the parallels become uncomfortably obvious. Which is why we need to emphasize the absolute need for a deity for something to be a religion, and the absolute conformity that every adherent is forced, compelled, to be subject to. Even if things like Buddhism and Taoism aren't really religions (and I've heard that argument made, even as the same arguers turn around and argue that they still deserve all the rights of religious freedom because they religions; in other words, they're both A and not-A, depending on what's being argued or, more often, who's being argued with).

What's funny is that these are the kinds of ideas floating around in religions, strictly defined. "We're free to worship, and all came to this willingly. There's no compulsion. Unlike that group over there, who are deluded, don't know how to think, and only stay because they're scared or there's something in it for them." In other words, Xian groups often sound like very much like secularists or atheists in describing their opposites.

This is a human thing. We self-organize in a limited number of ways because those are the ways that fit the psychology we have. There are outliers, but most people, even most of those considering themselves outliers, participate.

which are mostly or completely non-theistic, even in red Kansas...

https://en.wikipedia.org/wiki/Unitarian_Universalism

https://www.theatlantic.com/politics/archive/2016/09/oasis-secular-groups/499148/

I've been to both here in Wichita and thought they were something like what you describe.
As far as getting lots of people to join up, that will be a tough road in our fear based societies. imo...

There are also many service clubs and other groups. Most, however, include some sort of religious content in their meetings.

I have to disagree with your premise here.

"I believe that many, many people attend church and continue to call themselves Christian only for these more secular reasons. Not because they truly believe in the mythology of the Bible anymore than they believe in Santa."

I believe that the people you describe attend church and call themselves Christian because they believe in their version of Christianity, whatever that is. It allows for a moral superiority and lets them feel better about themselves and their actions as opposed to the secular reasoning you indicate.

As to their belief in Santa, not sure about that one.

organization. You can join at the district, city, or county level and be as involved as you wish. If you want to, you can also participate at the state and national level by becoming a delegate. That can take a little time to establish yourself, but it's not that difficult.

It will give you the community, fellowship, sense of belonging, and an opportunity to serve your fellow humans in a positive way.

It can even lead to becoming a candidate for local or other offices, where you can serve even more directly.

It's called kindness. Some of us have been trying to remain faithful to the only tenet. BE KIND.

But the GOP hates unions for economic reasons.

Interesting question.

Recommended.

Charity can be found in some atheist groups. I belong to two. There are also FB atheist groups.

would you be more selfish, self-centered, and likely to abuse substances?

The OP hasn't supported the premise that the problems listed have any relationship to whether people experience "The community, charity, the fellowship, the sense of belonging".

Community. Fellowship. Belonging. And I get pizza and beer.