Why naval laser defence is more than a power-supply problem

Are naval laser defences only a distant prospect until power and computing improve dramatically?

No. Limited systems were already viable, but practical compact weapons still depended heavily on better optics and lens design as well as power density.

Laser defence did not have to wait for an entirely new level of computing and power generation. Limited systems had already reached ships by the time of the stream. The harder step was shrinking a useful weapon into a practical naval installation. Lens design and shaping were major constraints alongside power supply.