Axis naval flak and Japan's missing mid-range weapon

Did every Axis navy suffer from the same weak shipboard anti-aircraft defenses?

No. German and Italian flak was not uniformly poor, while Japan's 25 mm system left a mid-range gap that industrial and logistics constraints made difficult to correct.

The claim that all Axis navies had poor shipboard flak draws a distinction between Germany and Italy on one hand and Japan on the other. Japan's 25 mm weapons left it needing a 40 mm system, despite having an Oerlikon-derived 20 mm weapon in production for the Zero. One assessment is that Japan entered the war a year earlier than it should have and should probably have bought Bofors guns. Building them would still depend on production and quality control. Late convoying and an insufficient remaining merchant fleet compounded the difficulty of sustaining the empire.