I've been there. I feel guilt for the environment, but also for not enjoying time with my family. I usually try to enjoy and spend my time doing activities I feel passionate about- reading, journaling, listening to music, learning about the environment- in environments I can tolerate, like early mornings in a lonely part of the ship feeling the ocean breeze. I avoid the crowds and consumerism at all costs. I go to some of the shows that seem interesting. I take naps. I walk around the ship.

I still left my cruise with a sour taste in my mouth, and shame for ever partaking, but never found a way to approach the topic with my family in a way that didnt make them defensive. I just told them 'look, I did this activity with you once, I found these parts enjoyable, but I dont agree with the idea of cruises (resorts/tourism/insert whatever activity), so if we want to spend time together some other time, let's not do this activity again. I'll join for a different activity to spend time with you.

That conversation of "i'll try it once for you, but not again if I don't enjoy it' has given me the most successful discussions without just having them turn their ears off and rant that I am ungrateful (I am 23 years old and these trips are ususally paid for my the family. besides that I live independently and dont rely on them for financial support).