A company's shareholders don't get explicit control over the entire economy or anything so absolute, they simply speak with whatever control they have over the private organizations that then, themselves, indirectly influence the economy.
I don't think 10% of America should literally have extra voting power in elections, and despite your allusion, they do not.
No matter how much you decry "money has influence in elections" people are free, in a democracy (as implemented by the US), to vote how they want. Any argument around, "People get manipulated" is a non-starter; as long as nobody is literally casting their ballots for them, they are free to choose to harm themselves. It's stupid of them[1], but that's democracy for you.
[1] https://en.wikipedia.org/wiki/Carlo_M._Cipolla#/media/File:C...
But even ignoring this point and going back to an idealized world, maybe I'm misunderstanding you -- can you spell out what you mean by "guide the economy" or making decisions about the economy?