The decision about how much UBI is enough and from whom it is drawn and by how much is the critical part of the equation, and that is necessarily centralized.
Indeed, only the state can succeed at decentralization. That's why we need some amount of centralized, democratic decision-making as well. But redistributing wealth as UBI is a good way to redistribute power across society (an unalloyed good -- power should be broadly distributed) while avoiding most of the worst parts of central planning.