Flettner Rotor Sails Again?

This is s fallacy and oversimplification. C_L and C_D are highly coupled. Its just a matter of finding an optimum for a given wing configuration. If you simplify to just looking at C_L and then leave the rest to best effort, you are probably not arriving at the best configuration imho.

For these ship applications high C_L does seem useful as larger wing areas impose other limitations (eg moments, mass, weight, cost, height and handling). Also drag does not seem highly important.

Also the amount of energy invested to maintain the wing is hugely important for ships.