You do not answer the question: What are the things you can only do with "blockchain technology" that cannot be achieved with existing technology? The things you mention can already be done with centralized trusted databases, just as you said.
GP means to say that git can cover most use cases via Merkle operations/properties. What Merkle does is give a trustless distributed ledger. Mining/PoW allow fully trustless+anonymous while other methods are trustless in the sense you can create rules and identites leveraging signatures atop the Merkle in various ways and audit changes before voting, eg. PKI in my experience.
