GPT-4 seems like a "generic system" that essentially "understands our intentions"
I suspect that a lot of my disagreement with your views comes down to thinking that current systems provide almost no evidence about the difficulty of aligning systems that could pose existential risks, because (I claim) current systems in fact almost certainly don't have any kind of meaningful situational awareness, or stable(ish) preferences over future world states.
In this case, I don't know why you think that GPT-4 "understands our intentions", unless you mean something very different by that than what you'd mean if you said that about another human. It is true that GPT-4 will produce output that, if it came from a human, would be quite strong evidence that our intentions were understood (more or less), but the process which generates that output is extremely different from the one that'd generate it in a human and is probably missing most of the relevant properties that we care about when it comes to "understanding". Like, in general, if you ask GPT-4 to produce output that references its internal state, that output will not have any obvious relationship[1] to its internal state, since (as far as we know) it doesn't have the same kind of introspective access to its internal state that we do. (It might, of course, condition its outputs on previous tokens it output, and some humans do in fact rely on examining their previous externally-observable behavior to try to figure out what they were thinking at the time. But that's not the modality I'm talking about.)
It is also true that GPT-4 usually produces output that seems like it basically corresponds to our intentions, but that being true does not depend on it "understanding our intentions".