I don't see how UBI would materially worsen the lives of the chronically ill and those who cannot sell their labor. It's essentially universal welfare that allows anyone to survive whether they sell their labor or not. That gives you the ability to leave a job that is exploiting you. Without UBI losing your job means potentially becoming homeless.
I'd say that it isn't far enough, sure. I'd also say that food and shelter should be considered universal human rights that everyone has to by law have access to regardless of their circumstances. Which would itself provide many of the same benefits as UBI.
As an anarchist and a socialist I'd change almost everything about the way the current world functions. But as a direct thing that would improve the lives of almost everyone, I am very much in favor of UBI.