But my reaction from a gut level is, what's the value of human life if machines do all the important stuff for us, while also surpassing us in creativity, insight and discovery?
But why would they? There is nothing inherent in the idea of AGI that says they absolutely have to.
This is again the fallacy of the Singulartiarians, that once you have a very powerful piece of technology, it will take over the world and oppress mankind. Why does that have to be the case? Well, it doesn't- and if it looks like it's how historically things have played out, with other technologies, then maybe the fault is not with the power of machines of all sorts but with the mismanagement that comes with greed and its excitement by useful technologies.
In any case there is still nothing that supports the equation AGI = human oppression, right out of the box.
This is a research problem.
Your phrasing makes it sound like you think “Singularitarians” choose to believe that rogue AIs are a potential risk, rather than deriving that knowledge.
Those people are fantasists, at best, charlatans at worst.
Actually, I think I can answer this- it's the Singularitarians who promote this idea. Unfortunately, their fantasies have tained the meaning of "AGI", making it synonymous with an evil (or amoral etc) paper-clip maximiser and the like.
A much more realistic sort of AGI, on the other hand, one that we could turn on and off as we pleased, would be a great tool in understanding our own, natural intelligence. Or it might be the case that we'll only ever achieve AGI once we have a better understanding of our own intelligence.
In any case, there's really no reason to assume that AGI will necessarily replace humanity.