This is a valuable criticism of the capitalist economic system. Notably, economist Richard D. Wolff speaks about how the top 1 percent controlling the majority of the outstanding corporate shares is fundamentally undemocratic.
In a capitalist corporation, there is an election every year or so to determine the board of directors. Who is placed on the board of directors is determined through an election where one share is one vote. In this vein, a small number of people controlling the bulk of the shares grants them disproportionate power to choose the board of directors, who will then subsequently make significant decisions on what happens to a lot of resources and a lot of people.
The United States almost makes a fetish out of democracy, but its economic system is mostly undemocratic. If democracy is such an important principle, why not democratize the economic system?
Why let a small number of shareholders dictate most of the economic elections?