The million dollar (perhaps literally) question is – could @kentonv have written this library quicker by himself without any AI help?
But what if you only need 2 kentonv's instead of 20 at the end? Do you assume we'll find enough new tasks that will occupy the other 18? I think that's the question.
And the author is implementing a fairly technical project in this case. How about routine LoB app development?
Nobody is claiming that human's won't have jobs simply because "we have accomplished everything this is to do". It's that humans will offer zero economic value compared to AI because AI gets so good and so cheap.
If there is some magic $10k AI that can fully replace a $200k software engineer then I'd love to see it. Until that happens this entire discussion is science fiction.
I think you have multiple offers of that very AI dangling in front of you, but you might be refusing to acknowledge them. One of the problems is the way you opt to frame the issue. Does "replacing" means firing the guy hoping to replace him with a Slack webhook? Or does it mean your team decides they don't need the same headcount of medior/senior engineers because a team of junior engineers mentored by someone focusing on quality ends up being more productive?