I feel like I should respond to this, because it’s relevant to my interests, and you linked a thread that I was part of. So!
As far as I can tell, religion is, indeed, not about beliefs. Or at least, beliefs aren’t the point of the religion. The point has more to do with values, shared cultural traditions, and rituals that create a sense of group belongingness. (And if you’re a mystic like me, then religion is also about the experience of the divine, but I won’t get into that here.)
But that doesn’t mean beliefs are irrelevant to religion. If I remember correctly, Kevin Simler says that beliefs are basically just an ingroup shibboleth. You believe some crazy ideas for which there’s no evidence, and these beliefs imply you should practice laborious rituals and follow restrictive taboos, which provides a costly signal that you are, in fact, a member of the group. (I haven’t read the essay in a long time, so I hope this is actually what Kevin was saying.)
Anyway, I disagree with this! Or, at least, I don’t think it’s the complete story. If beliefs only existed to create an ingroup shibboleth, then it wouldn’t matter what a group believed, as long as it provided a costly enough signal. But in fact, you see different kinds of societies holding different religious beliefs, suggesting that the specifics of the beliefs are important. You have the different kinds of mythology that Joseph Campbell described, one for hunting cultures and another for planting cultures. You have the fact that monotheism tends to arise in conjunction with empires. All of this suggests that beliefs are doing something. Whether they actually drive the social technologies, or whether they merely reflect the underlying worldview of the people, it seems that a synergy is necessary between the society and its beliefs. (I should probably give an example. By “beliefs actually driving the social technology”, I mean, say, that people are more inspired to follow the emperor when they’re also worshiping a single, all-powerful god. By “beliefs may reflect the underlying worldview”, I mean that in an empire, people might say “hey, we have a bunch of separate city-states ruled over by a single empire; I wonder if all our separate gods are ruled over by a single emperor-god, too”.)
So anyway, I think that beliefs are important. And you actually have to believe them in order for them to work. (I’m using “belief” pretty broadly here – to include the doctrines of the Judeo-Christian religion, which are interpreted as historical fact, as well as myths that aren’t historically “true”, but which exist in a separate dreamtime as archetypes of the collective unconscious. I’m also including traditions. The point is, I mean “believe” in an emotional sense, not a factual one. Like, I, personally, believe in the myth of the dying-and-rising god. Let’s take a concrete example, like the song “Finnegan’s Wake”. I believe in Finnegan’s Wake. What does that even mean? I don’t believe it actually happened. But I believe that the story condenses and encapsulates some fundamental aspect of human experience. I believe that it relates to things that happen in my own life. I believe it emotionally, where I listen to the song, and in my heart I say “yes, this is true”. But it’s not a factual truth. It’s an emotional truth. (If someone pokes me hard enough, I’ll try to explain this in cogsci terms.) Anyway, I think maybe this is what your Christian friend means when she says she believes in God. Maybe she feels, in her heart, that he is real and the stories are “true” in this emotional sense.)
So anyway, I think beliefs are important, but they don’t have to be factual beliefs; they can be emotional beliefs. But in any case, these beliefs drive people’s actions and values. The beliefs inspire people to perform specific rituals. And if the beliefs were just ingroup shibboleths, and the rituals were just mechanisms for promoting group cohesion, then it wouldn’t matter which beliefs and rituals a culture chose. But no, the beliefs drive people’s values and influence people’s fundamental ways of life. Christianity comes with certain values (chastity, etc.), and people are inspired to follow those values because they believe in the stories (of the Virgin Mary, etc.). So if you don’t hold the beliefs, what’s to inspire you to keep holding the values? And indeed, a lot of ex-Christians have ceased to care about chastity.
Here’s the thing – it’s nice to participate in age-old traditions, and we shouldn’t just tear down social technologies willy-nilly (Chesterton’s fence and all). But times do change, and the social technologies will need to adapt. Scientific discoveries weaken Judeo-Christian religious beliefs, which weakens religious values and traditions, and the whole thing starts to collapse. Similarly, the circumstances of the culture change, and the values that used to be necessary cease to be important, and people start to think that the religion is pointless. (I’m sure there is still virtue in chastity, but not nearly as much as there used to be, back before birth control!)
I think it’s pretty much inevitable that over time, religions will weaken; their beliefs, values, and traditions will become outmoded. People’s experience of the religion will start to grow hollow, as yours did. And when the religion collapses (just like when an empire collapses), it will leave this void of chaos, where new conflicting belief systems can compete for power. I think this is maybe what happened during the Protestant Reformation, and it definitely seems to be happening now.
So anyway, I wouldn’t feel bad about abandoning an old tradition, if it’s no longer meaningful to you. I wouldn’t follow a religion just because “religion is a social technology, and social technologies are important”. You have to find something that resonates with you. If Catholicism is important enough to you that you want to keep attending, regardless of your lack of belief, then by all means, continue. If you think Catholicism has something new-fangled belief systems can’t provide you with, then that seems like enough reason to keep practicing Catholicism. But if you think you can take what you like about Catholicism, and use it to create a new EA-inspired “religion”, then… I don’t see any reason why not to. I don’t think you should resist that course of action just because it’s new. (I mean, creating a new religion / social technology is always a matter of trial and error, and it will likely take a while before it’s as effective as Catholicism is to its true believers. But new social technologies need to be created at some point. Participating in a venerable institution can be powerful, but creating a new institution is also a method of participating in the continuity.)