Interesting analysis.
I live in a Catholic country since I was born, and since the first screenshots of the game after the KS campaign ended, I immediately noticed how this game presents a distorted version of pre-counciliar Catholicism.
1) The relics: relics are kept in high regard in Catholicism. Small items and body parts, even if loosely connected to a saint, a righetous person or a supposedly miraculous event, are kept like holy items able to grant good fortune/special abilities.
2) The suffering: suffering played a major role in medieval Catholicism. Considering the premise that everyone is a sinner, the more a person suffered (by outer means or by self-flagellation), the more they were kept in high consideration. Things escalated to a point where there was a true obsession with suffering.
3) Beauty: the fact that people starve or live in extremely poor conditions, while massive cathedrals are built, is something that truly happened in the medieval period. Adorning the graves of the dead with gold and other precious things while having difficult to find food for yourself was one of the many apparent contradictions of that period.
All of this is perfectly portrayed in Blasphemous. Imho, the game is a big satirical hit at traditional Catholicism, to all its contradictions and downsides. If you enter an old cathedral or church in Italy, you'll see most of the things you've seen through the game.

Yeah, although there's a similar stab at the Spanish Inquisition as well. It almost seems as though the Inquisition is running the show in Blasphemous… which might explain how things got so bad…

I think it also interesting to note that Blasphemous includes many nods to Catholicism's weirder parts – like, for example, the mention of the pelican in the Pelican Effigy bead, which was regarded as like to Jesus, because it was believed that if food was lacking, it would feed its children with its own blood. Here the focus is more upon the blood than the selflessness, of course.