It should be up to the cruise line to determine what they do and don't allow on their own ship, as long as they comply with federal law. If there is a federal mandate for masks, then passengers on ships that are in US waters or at the docks should be masked. If there's a state mandate for masks, the same, with regards to docking at that state's ports.
But if the state doesn't FORBID its own citizens to vaccinate or wear masks, then they can't expect any commercial entity to forbid it - including cruise ships. They also can't expect cruise ships to require it, unless the state has an actual mandate for all commercial enterprises where the public gather.
I'm looking forward to cruising again. But we stopped cruising because we couldn't afford the luxury. Next time we can afford it, I'm thinking we'll go full throttle - elegance, intimate environment, first-class cuisine, higher staff
assenger ratio, on a river cruise.