trifusionone, there's an Old Saw that "Insurance is sold, not bought!" But, as I wrote, when there actually is a risk for which protection is desired (as opposed to, say, manufactured by a salesman ... )
I am not criticizing your decisions, which are now water over the dam. But if you met with a bricks-and-mortar travel agent, it sounds to me like you made cost-conscious decisions that, while quite reasonable, were not entirely in your best interest.
For example, (referring to your discomfort over the "unsupervised" portion of your trip), you could have bought the air tickets from the cruise company. Then, they would have thrown in your airport transfer, (in their annoying bus or van), and they also would have given you a phone number to call if one of your flights was cancelled. However, that would also have produced a commission for the travel agent, and "hidden" several charges for your trip that are now fully "exposed" for you to study and decide on. In case I'm not being clear, I'm talking about European airport transfers, air re-routing in case of flight snags, and most likely (I didn't read the brocure) taking you to the second city of the boat if you fail to board through no fault of your own.
Again, I'm not berating you for your choices - you may not even be aware that you "made" these choices. Now, you have the option to buy insurance against most of these "perils" (as they say in the insurance business.) In a way, you're better off, because by using a third party, you have protection against the bankruptcy of the cruise company or the airline. (I'm not saying that happens a lot, I'm just listing "perils".)
One reason I buy travel insurance is because my mother is 88 years old. Because I have read the boring, 20-page brochure from Travelex, and called the 800 number to clear up a fuzzy statement, I learned that the health of someone in my immediate family who is NOT going on the trip is NOT a bar to the "pre-existing condition" exclusion! That's good news for me. HER bursitis isn't a problem for MY travel insurance. Other companies may write their policies differently.