A number of sibling comments are pointing out that we're just increasing the level of skill necessary to do the available jobs, drawing analogies to the industrial revolution. I think a key bottleneck in this progression is the mental capacity of the workforce. Surely there are biological limits on human mental ability, and while we can definitely bend the rules (education, nutrition, nootropics if they actually work…
Interesting point. But it brings up that scarier part of AI. I believe AI will become better at humans at mental processes far before it will be better than human physical labor. For exactly the points you mention. This is already becoming true for many logistical industries. What happens if AI replaces all the high level decision making positions and humans are relegated to handling the low level "last mile" tasks?…
I think that computation tends to replace relatively unskilled labor, relative to the skill of whatever created the AI/algorithm/whatever. So right now we're in a situation where software people are automating jobs which are generally less skilled than their own. Which is a little scary when viewed from the haves/have-not perspective I laid out above, but is much scarier from the AI/meatbag perspective you're talking about. It's not so much a difference between skilled & unskilled labor as it is a question of where on the skill totem pole the algorithm's creator resides.
Regarding order pickers, I think that's just a question of economics. When lots of semi-skilled jobs have been automated away and you have thousands of people clamoring for any chance to be paid, it is frequently cheaper to have them do the work than to have a robot do it. Although Amazon did have robots pick orders this last holiday season, suggesting that perhaps economies of scale have finally caught up on that particular type of manual labor: