In order to accurately simulate a particular brain, we'd need the technology to (i) accurately read all the information encoded in a particular brain, which everything we know about the brain suggests depends on getting a snapshot of the state of 85 billion neurons - and chemical interactions of those neurons' constituent proteins - at a particular millisecond in time. (ii) manipulate matter (or write matter-simulating code) such that we duplicate the state of that brain at that time, and probably the associated body too, with sufficient accuracy for the biochemical reactions (or digital emulation of the biochemical reactions) continue to produce a patterns resembles the thought processes of the emulated brain in their outputs.

I don't think we need to invoke "magic" or vitalism or quantum brains to suggest that replicators capable of reproducing a particular state of a mind-bogglingly complex set of biochemical processes without significant information loss may not be a practical possibility in future. If anything, that sounds harder than achieving AGI or something approaching it via other means.

As for the hype about general AI, we're responding to a thread musing on whether we'll get "close" to achieving it this year.

Right, we think we can. But we don't know. I would argue that as we get closer to doing it, it will become a fact that we can (or we will find that we can't.) The fact that we still don't know for sure that we can (or cannot) is an indicator or a symptom of how far away we are from actually doing it.