Earlier quoted context omitted.
I can't get myself to agree with this. Indeed, it's true, horses don't create demand, but neither do unemployed humans. Our economy isn't centred around humans, it's centred around capital. Unemployable humans are as useless to it as horses, as they can't exchange their labour with capital owners (or become capital owners themselves). Unemployable people might want more, but will they get more? No, they won't.
I think there's two distinct ideas being discussed. Can people be unemployed because of structural, societal, or political reasons? Sure, and I think most people would agree. We have plenty of example of that happening - depressions, recessions, mass refugees, etc. But can people be unemployed because we run out of things for humans to do? That's what the video is arguing, but it won't be the case unless we've fully…
-- You'll always have something that some other human wants the human X to do. Whether that other person can pay human X sufficient money to make that activity their job is the question. And it seems plausible you'll reach a point where the answer will be no for a lot of people. You can call that "structural" if you wish but it seems related to the marginal utility provided by a given person and that goes down as one finds automated alternatives.