I read your first paragraph and was like “disagree”, but when I got to the examples, I was like “well of I agree here, but that’s only because those analogies are stupid”.
At least one analogy I’d defend is the Sorcerer’s Apprentice one. (Some have argued that the underlying model has aged poorly, but I think that’s a red herring since it’s not the analogy’s fault.) I think it does share important features with the classical x-risk model.
Not the OP, but a point I’ve made in past discussions when this argument comes up is that this is would probably actually not be all that odd without additional assumptions.
For any realist theory of consciousness, a question you could ask is, do there exist two systems that have the same external behavior, but one system is much less conscious than the other? (∃S1,S2:B(S1)=B(S2)∧C(S1)≈0≠C(S2)?)
Most theories answer “yes”. Functionalists tend to answer “yes” because lookup tables can theoretically simulate programs. Integrated Information Theory explicitly answers yes (see Fig 8, p.37 in the IIT4.0 paper). Attention Schema Theory I’m not familiar with, but I assume it has to answer yes because you could build a functionally identical system without an attention mechanism. Essentially any theory that looks inside a system rather than at input/output level only—any non-behaviorist theory—has to answer yes.
Well if the answer is yes, then a situation you describe has to be possible. You just take S1 and gradually rebuild it to S2 such that behavior also gets preserved along the way.
So it seems to me like the fact that you can alter a system such that its consciousness fades but its behavior remains unchanged is not itself all that odd, it seems like something that probably has to be possible. Where it does get odd is if also assume that S1 and S2 perform their computations in a similar fashion. One thing that the examples I’ve listed all have in common is that this additional assumption is false; replacing e.g. a human cognitive function with a lookup table would lead in dramatically different internal behavior.
Because of all this, I think the more damning question would not just be “can you replace the brain bit by bit and consciousness fades” but “can you replace the brain bit by bit such that the new components do similar things internally to the old components, and consciousness fades”?[1] If the answer to that question is yes, then a theory might have a serious problem.
Notably this is actually the thought experiment Eliezer proposed in the sequences (see start of the Socrates Dialogue).