On the protocol side, bitcoin got just more decentralized with the fight between classic, Core and BU, because it wasn't and there was leadership, but there isn't much any more, which is good.
The ability of miners to 51% attack the protocol is not decentralization. To paraphase Benjamin Franklin in our context, those who would trade a huge loss of decentralization in the functioning of the protocol for a tiny morsel of decentralization attacking the protocol immutability, deserve neither decentralization nor protocol adaptability.
The root problem is that Satoshi's design isn't sufficiently adaptable without centralized control.