I guess the social function of religion is to maintain social cohesion by suppressing urges that lead to individuality (such as sexuality, magic and mysticism) and providing rituals to guide people through the trauma that this will inevitably create. Examples: the way that mystics, magicians and sexual and gender-variant individuals are shunned and persecuted by religions. Also, rites of passage are designed to negotiate the tensions created between individual impulses and the needs of the group. This is why they take place at times of stress.
This is all very well if the religion functions to maintain a just society, but not if the society being maintained is fundamentally unjust. I also suspect that all esoteric systems will eventually settle down and become religions in that sense - which is why Aleister Crowley rejected the idea of "Crowleyanity". He knew that his path would be turned into a religion for others to follow, and wanted to prevent that.
If you look at the way religious movements develop, their eventual assimilation into the host society is all too frequent. Sometimes they influence the host society, but all too often the reverse is true. Religions start out radically counter-cultural, and then gradually assimilate. If their rules are particularly demanding, this is probably a good thing, but in many cases, it's a bit of a disappointment. Christopher Partridge describes the assimilation process particularly well in The Re-enchantment of the West.
Of course, there are many values promoted by liberal religions which are worth having, like celebrating diversity, radical hospitality, community, and so on. But they still tend towards the sacrifice of individuality for the greater good.
Sometimes it can be painful to be in community with others. There's a certain element of impersonality about it. There is also an expectation of serving the community, and this can be in conflict with individuality, even in very liberal groups.