How did the Sendai-to-Agano gap affect Japanese light forces?

How did the long gap between the Sendai and Agano classes affect Imperial Japanese Navy light forces, and what filler design might have helped?

The gap sat inside a doctrine that expected cruisers to scout and support destroyers before a decisive battleship action, while treaty categories constrained a cleaner solution.

Japanese and American light cruisers were both shaped by an expected Pacific fleet battle. Their cruisers needed to scout, support destroyers, and fight enemy light forces before battleships supposedly decided the main action. Treaty categories encouraged both navies to adapt a cruiser model largely driven by Royal Navy requirements to very different Pacific needs. The passage raises the question of why Japan did not seek to exchange more light-cruiser allowance for heavy-cruiser tonnage at the London conference.