Christian missionaries have never gone on mission to accept people. They go on mission to convert, absorb, and indoctrinate people, and then exclude those who refuse. Look at what the Spanish missionaries did in California to the natives... they either got with the program and became good Christians, or got clapped. Sure, it's less violent today, but still highly exclusionary.

Christian missionaries operate under the assumption that non believers are excluded from heaven which is fairly patronizing. Christian lore was often used as justification for economies of dispossession (colonialism, slavery) in the modern European world.

Generally Eastern religions are more adaptable but they are also exclusionary in their own way. Buddhism was born out of Hinduism because of disillusionment with caste/ritual purity and ancient norms around animal sacrifice. Buddhism itself is exclusionary depending on how devout you are.

Generally speaking, every belief system / culture has "puritans" that perceive themselves as superior due to following a "less contaminated" or more traditional path. Nazism would be an example that does not have a strong religious basis.

I personally believe religion has two purposes 1) Giving people a sense of meaning in life and 2) Getting them accustomed to submitting to top down authorotarian structures (especially monotheistic religions which are often less decentralized). I think religion has acted as an important pacifier for people who felt fear and anxiety living a life of existential uncertainty, especially in pre-Modern times.

I think religion still has an important role today in helping people find meaning. I think it's good for people to explore their own spirituality. But as soon as one's spirituality devolves into seeing others as lesser, it loses both meaning and purpose.