When I am not on a ship I have more control in my environment and choices. For instance, I can choose to eat outdoors at restaurants, which I always do. I can walk in fresh air in parks. I can make decisions about the number of people I wish to be around by choosing the places/experiences I go. Just examples that obviously do not eliminate the possibility of becoming ill, and certainly knowing some people are not vaccinated. It’s just my way of reducing the opportunity.
On a ship many of those choices are not there. It is a more enclosed environment, and i personally feel that the more safety measures to counteract or reduce chances of Covid, the better - including required vaccines. JMHO. If the cruise lines all choose to follow this path, we will likely sit it out for a bit, do land travel, and then make a better informed decision based on the outcomes of those actions/new and more lenient rules. Maybe the impact won’t be so great. I have no idea. I just know my own comfort zone.