the point is that humans have subjective experiences in addition to, or in place of, whatever processes we could describe as information processing. since we aren't sure what is responsible for subjective experiences in humans, (we understand increasingly more of the physical correlates of conscious experience, but have no causal theories that can explain how the physical brain-states produce subjectivity) it would be presumptuous of us to assume we can simulate it in a digital computer. It may be possible with some future technology, field of science, or paradigm of thinking in mathematics or philosophy or somwthing, but to assume we can just do it now with only trivial modifications or additions to our theories is like humans of the past trying to tackle disease using miasma theory - we simply don't understand the subject of study enough to create accurate models of it. How exactly do you bridge the gap from objective physical phenomena to subjective experiential phenomena, even in theory? How much, or what kind, of information processing results in something like subjective experiential awareness? If 'consciousness is illusory', then what is the exact nature of the illusion, what is the illusion for the benefit of (i.e. what is the illusion concealing, and what is being kept ignorant by this illusion?) and how can we explain it in terms of physics and information processing?

it is just as presumptuous to assume that digital computers CAN simulate human consciousness without losing anything important, as it is to assume that they cannot.