GarfieldTravels

The poor guest services desk on Anthem last week...there were multiple parents screaming at them because their kids couldn't get off the ship.  It's amazing how many people didn't read any of the emails or info on Royal Caribbean's website prior to sailing.  

Without being privy to the communication you had with Royal it's hard to know where the confusion came from.  
Unvaccinated children can get off in Nassau... as long as they are booked on an excursion through Royal Caribbean.  Other cruise lines are doing the same thing because they have to and other internet sites have similar stories where people didn't understand the requirement to book a ship tour to leave the ship.  
Some ports require a ship tour for vaccinated guests too.  That's not the cruise lines adding that for specific ports, those are the regulations created by the country being visited.  St. Kitts, Barbados and St. Lucia have established this requirement for vaccinated and unvaccinated guests.  
It's unfortunate you were not clear on the requirements for Nassau.  

Poster DOES not say he booked an excursion, he booked cruise with RC but at no point is excursion mentioned 

This has been the policy since the restart of cruises.  It is a CDC requirement and is followed the other cruise lines that allow unvaccinated children. It is clearly listed in the many emails that you surely received before your cruise and has been discussed many times here on this website.  All you needed to do was book a tour through Royal and your son would have been able to go on the tour.
Keep in mind that the cruise lines need to follow both the CDC guidelines and the Covid rules in each port that they visit.  We may disagree with the policies, but they are all clearly communicated.
Tours Required for Families With Unvaccinated Children
Families traveling with unvaccinated kids must purchase a local tour through Royal Caribbean if they wish to go ashore in ports of call. This applies to all ports of call except Perfect Day at CocoCay, Labadee and Port Canaveral, Florida. Vaccinated parents wishing to go ashore freely can visit our youth facilities onboard to learn about drop off program hours and availability, and reserve time for their child on the day they wish to go in port.