Yes there are challenges like centralization within decentralization of blockchain. And you see in most of the cases the consensus is at the cost of decentralization of the blockchain. Some blockchain projects compromise with the decentralization little bit to enhance and improve transaction throughput of the blockchain. But this is a functional part of the blockchain. There are other use case also where the small group of people make centralized hubs and try to influence & reap the benefits as much as they can. In PoS consensus mechanism too, you can see a lot of centralization as that is stake based. So if you have staking power you can make it centralized.
Here are some examples of centralization in decentralization:-
Let's take our own Blockchain's example, large stake is held by few people.
maybe one of them can be taken or follow how to manage shares. because stocks are almost the same as digital money that doesn't seem to make this program sustainable