First, twenty thousand years or more of human history is about us trying to make other humans into machines: slavery, rape and forced prostitution, political coercion, war, overreaching prison systems and draconian punishments for minor crimes. We're not very nice to each other. Rather, we're controlling assholes as a species. Most of the ones who get power in organizations small and large are more focused on relative dominance than on absolute gain. From the Epic of Gilgamesh to the Bible to modern Stalinism, we see that effort by powerful people to turn the rest of humanity into a machine that will exert their own will.
Given 20,000 years of abusively turning humans into machines, tearing apart their families and banning their religions, attempting to boil them down into simple working devices, is it really likely that a control-freak species like us is going to let a machine try to assert itself as human? In peacetime, I think we'll be pretty good at preventing that from happening. We're good at mechanizing labor and, now that we have devices that outperform us at menial and dangerous work, that's becoming an asset rather than a flaw.
Sure, it's possible that we get outdone by AI, and in fact there's one context in which it's likely: war. Counted among the casualties of an all-out or existential war are all the rules that people once believed in, and all of our assumptions about what humans (who, normally, aren't so terrified and desperate or so power-hungry) will do. If a runaway AI destroys humanity, it will probably begin from humans warring against other humans, and in an all-out conflict where surrender is not seen as possible by either side.
This is not to downplay the risk. At best, I'd be saying that AI isn't dangerous in the way that guns aren't dangerous-- and, of course, we know that guns are extremely dangerous when used by humans to kill other humans. Luckily, this desire to kill another person doesn't seem to exist at the scale that would enable the existence of guns to be an existential threat.
So why might humans tend to kill other humans? Crime often results from scarcity. Well, technological unemployment is only accelerating. What happened to agricultural commodity prices in the 1920s, leading to widespread rural poverty and a global depression in the 1930s, is happening to almost all human labor today. It's terrifying because ill-managed prosperity begets scarcity and that begets fear and authoritarianism and war. While we're decades away from being able to build a species-killing AI (which, of course, would typically not be designed as such; it would probably be designed to kill some humans before running amok and doing fatal damage) I do think that if we are similar in character, by that time, to what we are now, it's a real threat. Power accrues, in most human organizations, not to those who deliver progress but to those who create scarcity. If this doesn't change, then wars will never end and that fact alone is an existential risk.