The system that allows billionaires to exist is capitalism, however Cortez seems content with the economic system as it is, save for a few reforms. Sad to see that she's just focused on moralising as usual
Wealth inequality isn’t even the primary problem; it’s a side effect. The primary problem is the inequality inherent to the power distribution within capitalism; a system wherein the mass appropriation of labor power, and the “profit” derived from capitalists not paying laborers the full value of their labor (calculated as value upon point of sale). It’s mass theft reinforced through a system of coercive contractual employment (sell your labor or don’t feed yourself/family). So long as the capitalist/proletariat or employee/employer relationship exists, then so, too, will entrenched inequality, a lack of democratic power in a more immediate part of your daily life than government (your job), no control over what you produce (alienation), and countless people being accused of moral failure to excuse the systemic failures of capitalism to meet basic human needs.
I agree with you. I was pointing out in my original post that, if Cortez's main issue is with "billionaires", she's (1) addressing the issue improperly, and (2) focused on morality politics. The only thing I must stress that it's one labour-power that is being sold, not labour itself. Otherwise, you understand the essentials of Marxian economics, something I wish could be said for others here.