Yep, they literally cannot work any other way than as a ponzi scheme. Because the people “earning” want to take more money out of the system than they put in, and the company is taking money out as well just to keep the game running and the employees paid, as well as to make a profit. So you need substantially more suckers buying into the system than the money that is being paid out.
Eventually, somebody is gonna be left holding an empty bag.