I think people put a little too much weight in the Castaway Club levels honestly. Aside from the Cabanas (which I personally don't really see the crazy draw to) most things can be attained by a silver level member. Most first time cruisers don't know what they're missing with Palo and such but even Palo can be booked by a first time cruiser in some cases.
So most things can be booked on your second cruise. Your first cruise there is so much you're trying to do honestly you may not even miss it. My first cruise the only thing I was bummed I couldn't get was a scheduled character meet. I quickly realized it wasn't a big deal tho because we met all the characters with very minimal wait times on the cruise. (as a new cruiser I thought the ONLY way to meet them was the scheduled meet)
I am sure the shorter cruises are more profitable for Disney. In that aspect the levels make sense. Plus also if you're on a short cruise often people will tie it to a WDW trip making it even more profitable for Disney.
I think first time, newer, Disney cruisers are already being discouraged . . . they can't book cabins until after all the plat and gold passengers. They have to work hard to get into Palo or tastings and don't have a chance at a coveted Cabana. I think there are ways to reward loyal passengers that doesn't take away from those at the bottom of the ladder. That said, there are a lot of other cruise lines out there. No one has to put themselves into the expensive quest for platinum and concierge.
For us on our first crusie tho honestly we didn't care about not being able to book those things. I'm the weirdo that still thinks the cabanas are a waste of money LOL!
My first cruise was a short one and I was more focused on doing things with my kids so personally I didn't really care too much about Palo, tastings or the cabanas. I also tho honestly didn't really know about them until I was on board.
Waiting to book doesn't really bother me either. As a first time cruiser I didn't really care all that much which ship I was on (so for the first timers and the Wish it may not be as big of a deal as you'd think). We booked much closer to time than when the cruises were first announced anyways so it was already well past all the CC levels.
First time cruisers really don't know all the perks and benefits and may not even know what they're missing honestly. Most travel at this point we know have rewards systems. This is true for so many things: Cruises, rental cars, air travel, hotels, etc. At this point I think its an expectation that places have rewards programs and most new customers aren't crazy mad about it