All wealth is the product of labor. But we are living in a world where the laborers do not own the wealth they create. Instead, we are living on a planet where the few, idle Capitalists own the majority of wealth.
We the workers are responsible for all wealth. But we are completely excluded from owning or managing this wealth. We aren't allowed to direct how the means of production are organized, or what they're organized for. We aren't allowed to receive the whole product of our labor, since a Capitalist exploits us to support their opulent luxury. From the hours we work to the products available on the market -- nobody consults the creators of wealth on how productive property should be organized and directed.
There are some who argue that workers alone aren't responsible for all wealth. They'll say that workers need machinery and land, provided by the Capitalist, to labor and create wealth. These people forget that the machinery was made by the workers -- and the land, itself, was made useful by the workers. These aren't things "added" by the Capitalist; they are things exploited out of their natural creators -- the working class. It is similar with innovation, where companies steal technologies created by their employees -- from the earliest machinery to Nikola Tesla's automobile engine.
Everything in society is created by the workers. Why, then, is it that the workers are the least benefitted from this wealth? It is because of the Capitalist system! If workers were to manage the businesses themselves, they could organize the industries for the benefit of all. Instead, we are living in society where businesses are managed by the few -- so, they only benefit the few.