Just a thought. Of course its decentralised by an order of magnitude compared to fiat or other alternatives, but what about the process/team that decided the 21 million coin limit for example? How are such rules changed by the way? Is it the same dev team that pushes changes to the Core release that decides these things?
For a certain point of view miners decide to adopt a new change. they are acting as a central entity able to make a decision for the whole protocol.
Likewise adopting segwit
https://charts.woobull.com/bitcoin-segwit-adoption/ has been evaluated and voted day by day while forging new blocks.
Not all change can be implemented in bitcoin rules since hard fork are always not permitted (create more then 21 millions of coins is one of the list)!