Holism means that for virtually every observation you have to update everything in your network, related or not. You cannot have nice networks with a bunch of small elegant compartments - it will be one huge mess.

My point is that actual Bayesianism is so insanely far beyond capabilities of any imaginable being, and Bayesianism with any assumed independence is no longer correct Bayesianism, that it's not really proper to pretend we're Bayesians in any practical sense.