it is the distribution of "power" not distribution of "load". the power to make decisions, enforce rules, keep the employees (eg. miners) in line with those rules,... the fact that each node does all of this on its own means they are not relying on anybody else and make their own decisions hence keeping the network decentralized.

Replication distributed system might describe better characteristic blockchain where all nodes do same thing (store same data, have identical/compatible rules, etc.).

Maybe sharding is what you're looking for since each nodes only verify and store some transaction/block.