Why Gefion was not a productive learning ship

Can Gefion be defended as an early design that taught Germany how to build better cruisers?

No; Gefion is not presented as a meaningful developmental prototype.

A viewer suggests treating Gefion as an early attempt that helped Germany learn how to design better cruisers. The reply rejects that defense without qualification. A purposeful experimental prototype differs from a ship whose compromises fail to create a coherent development path. Not every unsuccessful warship becomes valuable merely because later designers can observe what went wrong.