It's not only about god. Humans have direct immediate access to the contents of their own maps, while all information about the territory is suspect because it comes through the unreliable senses. This can easily lead a wannabe philosopher to stop trusting their senses and treat their own mind as a trustworthy separate magisterium (because they have a separate access to its contents).

Attributing the same thing to god is merely a patch to the problem of "my mind (but not yours) is special to me, your mind (but not mine) is special to you, but speaking objectively, maybe minds really are not special at all". You can avoid this conclusion by making a logical jump to "well, it's the God's mind that is really really special!"

But this does not actually address the essence of the problem, which is that my (human) mind is not special, and... well, the whole chain of thought was started by the assumption that it was. So when we know the original idea was wrong, why follow the chain at all?

(Funny thing is, living things are built from DNA blueprints like you described, so that means that ironically evolution is the only place where the idealistic approach is kinda correct. The only problem is that the blueprints themselves are also subject to change.)