tytanowy explanation is the closest to what i believe count as decentralization. however, some people decide to separate voting power/decision making and network, which sometimes result in a blurry debate. it is apparent when people talk about how bitcoin is centralized because most miners are running their rig in china, and so on. imo mining location is not the core of the decentralization, since you can easily remove one location but the network is still going to survive albeit the scalability might be affected in short-term.