I'd rather not go into any details but I dislike how it portrays religion and the Church, it's ignorant and disrespectful to the source material just because the director has a massive hate boner towards religion.
Also he never played the games so fuck him.
It is somewhat period accurate. Not saying all Christians are like that or were like that. There is no denying stuff like the Salem Witch Trials, Holocaust, Spanish Inquisition, Colonialism etc. I am just stating historical events in which Christians did bad things.
Christians have done good things though like providing food and nourishment for developing countries. Castlevania chose to focus on the dark side of religion because it is more compelling and adds to the ambiance of what they were going for.
We can't really discuss more than that as I am already walking eggshells around politics.
However plenty of other celebrated media bashes religion and seemingly gets a pass from fans from JRPGs to WRPGs and onward.