There is something profoundly unseemly about a group of well fed academics debating the relative misery of billions of people, none of whom has the slightest chance of ever living in the way that we do. So, let us stop.
As a Marxist, let me stipulate that capitalism has been an enormous step forward for the human race, both by dramatically expanding the total physical output of the world's economy and by undermining religious supersititions and traditional ways of life [although unfortunately not enough]. So if anyone feels the need to give Brownie points to capitalism, to give it a gold star, feel free. No serious Marxist will dispute you.
It is indisputable that in the present capitalist world order, there are enormous disparities of wealth and poverty and very great misery abroad in the world.
If you think that capitalism is the only alternative to feudalism or slavery, then your only concern, if you feel one, will be to figure out ways to ameliorate some of that misery. If you do not feel the slightest concern for that misery, then I have nothing to say to you. Go your way, and try to stay out of trouble.
But, suppose capitalism is not the equivalent of rationality. Suppose that just as capitalism grew out of feudalism, so perhaps something different can grow out of capitalism, something even more rational, even better at serving human needs and avoiding the periodic crises, such as the one we are now in. Then I for one want to figure out what that is and work to bring it about. I do not expect those who have benefitted the most from capitalism to join me in this struggle, although some may. But I can at least hope that those harmed by capitalism, those impoverished in the face of its outpouring of goods, those who have no option but to take a bad job, rather than the even worse job or no job that would otherwise be their lot, will join with me, or allow me to join with them, in the fight.