I am pro cruising and have cruised for 30 total nights (14 nights on Carnival) since the restart. However, I have a more balanced opinion of cruising and vacationing. Both passengers and crew are testing positive, all the big lines are using passenger-less ships to quarantine the crew with Carnival using the Sensation. On the macro level, cruise ships are notoriously crowded with the majority of venues being indoors. In many cases you simply can't avoid waiting in crowds/lines to get into venues and if you want to social distance, others around you may not. They tend to still pack those dining next to each other vs spacing folks out. Mask enforcement was incredibly weak, while crew would "suggest" folks to mask up, if passengers ignored their "suggestion", there were no further action would be taken. Now specifically for Carnival, unlike the other lines, they elected to sail with the industry highest capacity and are the only cruise elected not to hire extra staff to staff serve the buffet. YMMV, yet on my 30 nights as recent as three weeks ago, this was my direct experience. I own it, it is a calculated risk I take.
During the pandemic, I have stayed in all inclusive resorts in Cabo and Playa Del Carmen. In both locations, almost all venues were open air, plenty of properly spaced out seating in all venues. On a cruise, I witnessed a passenger not wearing a mask from the aft of the ship to the middle where the MDR host was located, passed several crew who didn't say a word. Once at the host stand, the host said to put on the mask but then the waiter said follow me and sat them down without them ever putting on a mask. The only real enforcement I saw was at table games at the casino yet even during that time (they've now banned smoking from casinos) you could have a cigarette in your mouth and not have to wear a mask. In Mexico all inclusive resorts, if you're in one of the few indoor locations without a mask, first off you were halted. You'd next be asked one last time to put on a mask (or wear it correctly) and if you didn't immediately comply, they simply radio security.
There could be a lot of improvements cruise lines could make but they chose not to because it requires more costs due to staffing. Doubling the amount of shows and doubling the dining times (When they have a sea brunch, awesome. When they don't, MDR Lunch is usually only available for 90mins). Also I believe Carnival should staff serve the buffet.