To clarify, I'm not arguing that capitalism is inherently bad or that it hasn't pulled huge swaths of people out of poverty.
What I'm pushing back against (which I often see in discussions of UBI) is that powerful people will give out free money just out of the goodness of their heart or because "they'll need people to buy their products". We're transitioning out of an era where labor has held (historically) a lot of power, but now technology is heading us down a path where capital will hold the vast majority of the cards. And a lot of the discussion around stuff like UBI just feels like hopium to me: "Surely with an abundance of riches we won't just let people die in the street!" But yes, we actually do let people die in the street already, especially if they're kinda far away.
The powers behind tech and AI are not going to give up that power willingly, or from the good of their hearts.