Maybe the cruise ships just need to run up a black flag and ignore the CDC. CDC can’t stop them once they are in international waters!
There are nasty viruses worse than Corona on cruise ships all the time and people still choose these types of vacations. Let people take care of their own bodies and make their own choices. This is absurd. The pharmacy on board can stock all the treatments for Covid of which there are several. Life is risky every minute of everyday.