I wouldnt want to risk going to find myself feeling insecure on a ship with people on board who arent complying and putting others at risk by their behaviour...so,
I wouldn't cruise unless onboard measures, hand cleansing, social distancing mask wearing were compulsory and part of the cruise contract. Everyone should have to comply, no excuses or exceptions etc. otherwise, like other behaviour issues they would be offloaded. It would be for the safety of everyone on board, crew and cruisers. If this meant some couldnt cruise for now, then they might have to live with that and chose another type of vacation. Just like those who are badly seasick wouldnt choose to cruise.
Her in the UK we are now starting to go out, but are choosing to go where we are sure of high standards, and compliant behaviour by those who frequent those places. Its working out well for us so far.
Wash (hands frequently)
Face (covering or mask)
Space (around 2 metres)
Act like you've got it and stop the spread