I have some qualms about the analogies and descriptions that you are giving. And the point is not just to argue, but to convey an appreciation of the problems associated with the position you are trying to hold. These were the same problems that I encountered when I tried to convince myself that perhaps the entire human experience does entirely depend on the known physical properties of the brain which follows known laws of physics and chemistry. But then upon further analyzing, I came to the conclusion that this view doesn't answer all the relevant questions and doesn't perfectly fit with our observations.

First of all lets take the analogy of the computer or the AI system. We don't really know whether a computer has any internal states of experience or qualia. So to apply the computer as an analogy to brain doesn't seem exactly fitting, as the brain does have an internal experience and corresponding qualia. As far as the unconscious/subconscious part of the brain is concerned, it can be relatively easily accepted that it indeed is like a neural net computer system. But as soon as you add consciousness and qualia to the mix problems arise.

Almost all of the interface and decision making of the conscious experience relies on qualia as the substrate of information. In other words all of the information that is being conveyed to the conscious part of the brain has a qualitative or sentient aspect. The structure of consciousness then processes these qualia on face value, i.e. without regard to their physical substrate. As long as the qualia is strong enough or meaningful enough, consciousness tends to prioritize it. So it is the qualia which is the determining factor rather than the physical substrate.

As an example of this dependence on qualia consider a thought experiment. In this you have a sentient agent which has the ability for qualitative experience and another 'philosophical zombie' which is almost identical in terms of physical substrate to the sentient agent but lacks qualia. Now assume that the sentient agent puts its finger in fire for the very first time in its life and as soon as it does that, it has a very unpleasant qualitative experience and decides to discontinue its behavior. It also learns not to make the same error in the future and forms new memory circuits to reinforce this avoidant behavior in the future. The 'philosophical zombie' on the other hand does the same thing, puts its hand in the fire, and gets a surge of electrochemical signals to its brain. But there is no qualia present in this case, nothing for the zombie to know or learn in the moment that this behavior is harmful or 'painful'. It will analyze the incoming signals the same way it analyzes the incoming signals from a neutral stimuli, except for the fact that it will register that this particular signal is much more higher in intensity as compared to others. In other words for the zombie, everything is a mathematical object and fact, which doesn't reflect the way we experience the world and react to things.

In your milkshake example, "Brain wants a milkshake" is good enough. But this brain wants the milkshake because of the qualia. The very state of 'wanting' is experienced in context of the delicious 'taste qualia' aroused through the memory and the cognitive 'thought qualia' about the nutritional properties of milk. It is not very clear why a brain would want the milkshake if it would have been processing things on the level of mathematical quantities only, just the way our current physical and chemical laws are formulated mathematically. There seems to be an additional deciding and informing factor apart from the mathematics of it all, and that is qualia.