That's the beautiful thing, different people enjoy different things, and on vacation, people get to pick and do the thing they enjoy, rather than the thing someone else enjoys.
Except with cruise ships, morally righteous people are declaring this specific thing wrong and trying to keep people from being allowed to do this.
The Guardian claims that "At full power the Harmony of the Seas’ two 16-cylinder engines would each burn 1,377 US gallons an hour" https://www.theguardian.com/environment/2016/may/21/the-worl..., which would be 5.2 cubic meters per hour, or 125 cubic meters per day, so something between 100 and 125 tons. Other sources I've seen claim "up to 250 tons" (https://www.colorado.edu/mechanical/2016/07/25/how-much-fuel...). A ton of diesel-like fuel produces around 2.6 tons of CO2 (the O2 comes from the air).
So let's say 750 tons. Split across 5000 passengers, a 7-day cruise would be 750 / 5000 * 7 = roughly one ton of CO2 per passenger per cruise.
Myclimate estimates the total footprint of a 7-day cruise, standard double cabin on a >4000 passenger ship, one day in port, as 2.1 t (this presumably also covers food etc. so it's not surprising that it's higher). They also estimate just the flight (one passenger, round trip, economy class) of a trip from New York to Maui as 3 tons.
You are cherry-picking only one of the environmental issues that cruise ships cause. Even that aside, you are also ignoring a large part of the discussion in the first article you cite, which focuses on all of the other, acute, air pollution cruise travel causes in the port cities. Focusing on CO2 is a strawman.
I focused on CO2 because it's often cited and one of the more comparable metrics, and I used those articles only as sources for my estimates. Between the date of the article and today, significant new regulation for maritime fuels came out.
But the kind of environmentalists I am talking about aren't suggesting to regulate cruise ship emissions, they demand banning cruise ships, because they're a visible symbol of loosely-defined luxury/"excess", and thus any impact is seen as unjustifiable.
There’s a different kind of serendipity that comes with Cruise vacations as opposed to road tripping, but it’s still very much there. Furthermore, I can’t really have a road trip experience with 16 people in my travel group; If we want to be together, we’ll be stuck, packed into a van. I can have a great cruise experience with a group that size on a cruise or at a resort.
I say this is someone who had taken multiple motorcycle trips across the US. Coast to coast on one of them and another down Baja.
And these have zero appeal to me as well.
As someone who road trips all across the U.S. with the wife, the highlights have of course been the serendipitous ones.