Marella also doesn't like it but have only said that in response to being asked - carnival have also made a statement. My view is it is fun as long as it doesn't go over the top (e.g. when one person bring loads and loads), when they are eco friendly and when care is taken hiding them.
https://bnnbreaking.com/lifestyle/carnival-cruise-line-bans-rubber-ducks-with-business-cards-and-homemade-goodies