Why capital ships stayed out of the Channel

Would improved 1944 technology have made capital ships useful during the 1940 evacuation?

Mines and undersea threats were the primary obstacle. Capital ships would have been used if a German capital-ship threat had required them.

The answer shifts attention from air attack to the wider problem of operating large ships in constricted, uncleared waters. Mine warfare, submarines, and torpedo boats made the Channel hazardous unless a large area could be swept and protected. Flower-class escorts, Hunt-class destroyers, and minesweeping forces were not yet available in the numbers needed to make that risk routine. He uses the same logic to explain why aircraft carriers were not required for D-Day: clearing a carrier operating area would have been a major commitment without a matching need.