>This means whoever writes (or wrote) the software controls the policy.

1. there are multiple competing implementations

2. it's ultimately up to the users/merchants/miners what software they run. A commit making into the bitcoin core repo doesn't mean it's going to be adopted by the network.

Bitcoin mining has also been centralised since about 2014 - three entities are known to control >50% of all mining, and there's no way of knowing how many of the other mining entities they have effective control over.

"Decentralised" is a phantasm.

Yes, similar to how the US presidential election is centrally controlled because only 51 entities are voting.