I agree that many go clueless, but I also think that is far easier on the cruise than at WDW. I mean, at the worst, all you've got to do is read a Navigator and figure out what you want to do, and wander around the ship until you find everything (which as we all know, is kinda fun). But, at WDW there's so much more to know --- resorts to stay in, where to eat (where NOT to eat), early entry, fastpasses, parades, fireworks, shows, and on and on. If you go clueless to WDW, I think you short change yourself, even if you have a great time. And the chances for frustration are higher.
That said, I'll never forget an eye opening experience on my first cruise. We shared a table with a family of four, or at least we were supposed to. They didn't come to dinner until the last evening. They didn't go to any shows, other than one late night movie. They spent all their time by the pool or on their verandah or on a beach at one of the ports, and they ate all their meals at the buffet or Plutos. And they said they it had been one of their best vacations ever! They loved the cruise as much as we did, it's the classic "different strokes for different folks".