I don't think they're either/or, they're complementary, and they use each product to cross-sell the other. Cruise ships also have a shorter lifespan and are associated with an asset that fully depreciates / becomes unsellable, where as a
DVC property is still on land, there's still something tangible at the end of the day.
The simplest answer IMO is that real estate has become prohibitively expensive for Disney to gamble on; the real estate market in general has become too efficient to extract excess returns relative to risk. For instance, Airbnb / VRBO fundamentally changed the vacation rental game and greatly increased customer expectations of a vacation rental. Only within the Disney bubble does Disney feel like they still have a differentiated product. And that's why I'd expect
Disneyland Paris to eventually get a DVC property or two. Would also make the DVC product "more exotic" if you could visit Paris on your Copper Creek contract (without using your points on a hotel stay with poor conversion rates for your points).