So it's been spreading, alot, and there are still people out there who participate on cruises.
It would definitely suck if you've already purchased tickets that can't be returned, but is it worth the risk of being quarantined on the ship? You'll be stuck in a tiny room that you may or may not need to share with friends/family or maybe even strangers. Not all rooms are designed for extended stays. A large portion of them might just be full of bunk beds and or without any windows.
Clean clothes would also quickly become an issue and there'll also be the dread and anxiety associated with being on an infested ship.
If you're young and health, you can decide for yourself if you want to take that risk. Just keep in mind that you might be endangering anyone you later come in contact with.