When we get complete neuronal connection maps (which we are getting close to for mice and humans will be done within a decade or two), we could in principle simulate a brain on a computer or on paper too. Unless you assert something magical like a "soul", these connections are what determine human consciousness. It is one thing to argue that LLMs don't resemble brains and if they could be "conscious" they wouldn't be conscious in the sense we are, but asserting that anything understandable can't be conscious won't age well.