I've heard that ZUN won't focus on Abrahamic religions because it would make the eastern religions seem bad compared to the true good western one. Doesn't Nirvana in Buddhism though require everything else to be fake and not real?
I've actually talked about the Abrahamic question before, myself.
Definitely never heard it put like "the Eastern religions seeming bad compared to the true good Western one", so that's either poor phrasing or you've been given the wrong idea. Might as well copy the relevant part from the SCoOW interview (every second line is the interviewer):
If you just mean how Buddhism as a religion and philosophy posits that all other pursuits are ultimately meaningless and the goal of one's existence should be its cessation and all that, yeah, that checks out. In that sense, Buddhism claims to be the "true, good" religion.
However, the essential difference is that putting aside philosophical discussions of what is "real", Buddhism is highly syncretic. It can easily not just share space with but actually integrate other religions, either fully acknowledging or coming up with its own interpretations of their deities and whatnot. It just then adds the idea that what you should be doing, amongst all these supernatural distractions, is pursuing Nirvana. Some of those deities may be willing to help you. This is especially pronounced in Japan, where Shinto-Buddhist syncretism was the religion for over a thousand years and remains in many forms to this day. The Abrahamic faiths only ever syncretize other faiths' gods in a rather, uh, let's say more "assimilationist" manner. It's a complex topic but the difference is clear.
It's just kind of a fact that practically all religions consider themselves "the true one". How monotheistic religions differ is that even on the most surface and everyday level, they're very difficult to square with other, polytheistic faiths in a way that isn't inherently adversarial (besides just agreeing to disagree, obviously, but that doesn't work so well when the gods are tangibly present in the story). Obviously all religions have e.g. mutually exclusive world creation myths and stuff like that, but especially the ones prominent in Touhou have a long history of sharing space and are easy enough to mash together into one fictional setting, at least at the level of detail and seriousness that they're usually discussed in Touhou.
The Abrahamic faiths aren't simply hard to fit in because they claim to be the bestest. They're hard to include, in practical terms, without either overshadowing the others or just seeming objectively wrong about the things most central to them, as I discussed in the older ask. And that's besides the other challenges that ZUN associates with using Abrahamic faiths in games.
While obviously none of them are perfect representations of their faiths in real life, you can easily put Kanako, Byakuren and Miko in a room and have them debate religious ideology for hours without ever needing to question each other's nature or even so much legitimacy, only their priorities within a pretty well shared basic world-view. You really couldn't imagine the same with an angel of God in the room. Or even a devout believer thereof.
