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…
Obviously true, but that doesn't mean the things still left to do can be done by anyone.
In a world where there's not enough food or housing, everyone can be gainfully employed, since just about everyone can learn to plant seeds or cut wood.
In a world where all of our material desires are already met, plenty of people will still want e.g. new AAA-quality video games every year. But what are the people who aren't programmers or artists supposed to do?