Even if you use some other consensus mechanism they're still inefficient. All full nodes in the network still have to propagate, validate and store all transact

Even if you use some other consensus mechanism they're still inefficient. All full nodes in the network still have to propagate, validate and store all transactions forever. This is indeed much more inefficient compared to a centralized solution and it's very difficult to create a decentralized network that can handle the amount of transactions that VISA processes for example.