On our recent, very full, cruise out of Southampton on the Silhouette the Captain announced toward the end of the cruise that the number of Covid cases had reached the threshold and asked that passengers wear masks in crowded locations and exercise caution. Some folks responded by wearing masks in the theater, casino and elevators, although many did not. Not surprising.
The thing that I did find surprising though, was that it was actually quite easy to maintain a reasonable level of social distancing while on board. Even though the Martini Bar was always packed (apparently Brits love their martinis π), we were always able to find another location that was much less crowded. The World Class Bar was great (maybe my new favorite). The early show in theater had plenty of seats to spread out and by the time we got to Blu each evening, the crowd had thinned and we almost always were seated with vacant tables next to us. The excursion buses were a bit of a challenge but even they were not full and we generally were able to sit in seats that were adjacent to vacant seats and wear our masks. So, all in all, we were able to reduce (not eliminate) risk without sacrificing having a great cruise.
As for the elevators, it seemed every time a really crowded elevator stopped and we would wait instead of making it even more crowded, the next one would be empty or nearly so.
As others on this thread have said, Covid is with us and will likely always be (although comparing it to the flu significantly understates the seriousness of Covid). But with a bit of effort, the risk can be reduced and thereby increase the chances of cruising without getting sick. The good news is that the same precautions one uses for Covid also reduce the risk of other contagious diseases.
Happy cruising.