There are mathematical reasons that billionaires probably represent a symptom of systemic problems. But most of the left does a shit job of selling this beyond hate of rich.
What really matters is that X percent being so far beyond the median eventually represents NOT production. It matters if someone is making money without production. If so, then we need to reexamine the system and tax and pay.
Capitalism needs to reward output not just positioning.
You and I are making data for amazon and/or Google right now. Where's our share of the work? How can you realistically opt out?
@Kneeblock does a better job than Bernie in discussing why people siphoning off and centralizing stagnant capital is a problem.
I tire of the demonizing of "them" (Bernie calling a million in salary or wealth "millionaires" interchangeably so lazy) but centralizing too much capital is an inefficient use of that capital. And it's also anti-capitalism as much as monopolies. It breeds instability, boom and bust, and eventually slows the economy with contraction.