In the West, Christianity remains the mainstream default religion (no mater how much my fellow Fundamentalists insist "True Christians" are a minority). So any work of fiction looking to be Anti-Religion (or at least anti Organized Religion) in general is bound to have Christianity specifically in mind more then any other.
Thing is, this perception often filters how we view media from other non Western Countries. Especially from Japan which has made a very notable mark on American pop culture thanks to Godzilla, Anime and Video Games.
Christianity is known enough in Japan that you see it referenced a lot. But still only 1% of the population identifies as Christian. The vast majority of those are Catholic though the LDS Church has enough clout in Japan to get three Temples built there including one in Tokyo. Still Catholic tends to be the default in how Japan views Christianity.
Japan doesn't even really define religion the way we do in the modern West. But the main faith in Japan remains Shintoism, with a strong Buddhist presence/influence. And Shinto is an organized religion with the Imperial Family being at it's head.
Religious/Spiritual themes are quite common in the Final Fantasy games (they are fairly unavoidable in the Fantasy genre) often in ways that seem to come down against at least Organized Religion. However Matt Pat of Game Theory argues it's against religion in general, often with the idea that if a God/gods does exist, It/they'd be Evil.
Often Christianity is very specifically in mind in Final Fantasy's religious themes, especially Final Fantasy Tactics who's Evil Church is clearly based on the Medieval Catholic Church. In fact the game allegorically makes Jesus himself Evil and Judas Iscariot a defamed hero. But it's a game inspired by English history, the War of the Roses (it's the Game of Thrones of video games).
Final Fantasy X and it's Yevon religion is often viewed as the harshest of all Final Fantasy games in how anti Religion they can be. And because of that people in the West discussing it constantly bring up Christianity.
The only Christian references I see in Final Fantasy X are the purely superficial uses of the words "Church" and "Sin". And that's going off the English translation, who knows how accurate that even is. But I'll give the Dub the benefit of the doubt on that for now.
Applying the word Church to religious contexts outside Christianity has become common, the term "Separation of Church and State" is not meant to apply only to Christianity. And the word "Sin" is not even necessarily Christian in origin.
The overarching theme of Final Fantasy X involves the Church of Yevon condemning Technology insisting Technology getting out of control causes us to become out of touch with Nature.
Western Atheists love to see Christianity as Anti-Science because Fundamentalists often disagree with mainstream modern Scientists on cosmological theories like Evolution. (And some fringe elements will argue the Earth is Flat, my thoughts on that are here.)
And from that will try to insist Christianity is bad for Technological advancement. But that accusation simply doesn't hold up. The first book printed on a printing press was The Bible. And that wasn't just a token gesture, the invention of the Printing Press was driven by the desire of Protestant Christians to end the Catholic Church's Monopoly on God's Word. And even in modern history, a Young Earth Creationist invented the MRI Machine.
The Nature worship aspect of the Yevon religion is actually quite in conflict with Christian values. Paul in Romans 1 defines Paganism as the worship of the Creation instead of the Creator. Many Christians have felt sympathy for such Nature worshiping sentiments, like J.R.R. Tolkien and maybe also C.S.Lewis. But that tends to be partly why those same Christians get heavily criticized by radical Christians for being way to Paganized (Jack Chick's infamous Dark Dungeons tract condemns them both).
The beliefs of the Yevon religion really do seem way more Shinto to me. Yuna and other female Summoners seem to be molded after Mikos.
And the whole Technology is bad for nature sentiment that Final Fantasy X is seeking to deconstruct seems to be exactly what Final Fantasy VII comes down in favor of. Which was definitely influenced by Shinto sentiments in doing so.
And even Superficially, all the Priestly Robes affiliated with this religion seem far more Eastern then Western in style.