Which infrastructure did Yonai think Japan lacked?

What infrastructure was Japan neglecting most in Yonai's argument?

Shipyards, dry docks, fuel facilities, and internal freight links capable of replacing vulnerable coastal shipping.

Yonai's priorities were more shipyards, more dry docks, larger fuel facilities, and stronger internal transport. Japan depended heavily on coastal shipping, so maritime interdiction could disrupt domestic freight as well as imports. Its narrow-gauge, passenger-oriented railways could not simply absorb that traffic, and several rail links still relied on vulnerable ferries. A fleet's endurance depends on national transport and repair capacity alongside the number of warships in commission.