> I'd make the argument that most people can become millionaires.

Make the argument then. How do “most” people become millionaires if that requires owning businesses or getting high up in a company? Who works for them if the majority of people are at the top?

Oddly enough I'd say the OP has a decent point were it not for that last part.

There are many more ways of making money, and the economy is not zero sum. And of course just because most could do it doesn't mean most will. Most of us can workout 3 times a week, that doesn't mean most of us do.