The internet (i.e., the cloud) is a collection of these closed systems interacting. The traditional client-server model delivers great scalability and faster iteration, but it relies on a monopolistic behavior with centralized control and single points of failure.
Web3 architecture is decentralized by design: blockchains are peer-to-peer networks. They trade technical scalability for social scalability. In this new paradigm, validators are incentivized to keep the network impartial. There is no single point of failure, and each client node owns its data.