Well, I think the "promise" was to replace fiat in a low cost and fast p2p payment system. That has failed to materialize in any meaningful way. Don't get me wrong, it still can happen. Just that it has not happened yet and the general public has not embraced bitcoin as a fiat replacement.
Decentralized just means that no one entity has control or large influence on the network. An entity could be a government, a company, a group, or a single person.

and having these kind of people lead us to the future is nothing less than a nightmare and the possible end for Bitcoin and all crypto. What a wasted chance all of this is ending up to be!