I believe you entirely. Best way to build immunity is to get a mild exposure to any virus. That is how I survived growing up in India which has plenty of viruses going around.
However when they are boarding 3000-4000 passengers in 3 hours on a cruise ship, there is not enough time to test every passenger. A vaccine document is much faster to process.
So yes, you may not need the vaccine. But you might miss out on participating in some activities.
“...there is not enough time to test every passenger. A vaccine document is much faster to process.”
So is a document saying that I had Covid.