It has a pyramidal structure like every crypto-asset. But it was not build as a ponzi scheme. This is not the problem. The problem is that the stake legitimates you in a way harming the fairness and equality. Early stake holders are lucky people but have no competence and there is no reason why their opinion should be over represented. But unfortunately it is. This makes the participation a buy to win game.

By observing Steem one can learn a lot about DAO like social medias. They are not social at all. Its not easy to change a running system. Once the power is distributed amongst a few big stake holders you have to convince each one of them. As as long as they make money by self-voting and abusing the Steem system, they wont listen to you.