Not on decor per se, but certainly the quality of the room itself. Value and moderate have always been more utilitarian and motel-like. The deluxe resorts have always tried to offer a more luxe experience and while the size of the room is important, the design features, materials used, the level of detail are all supposed to get better with each category... the same way a room at the JW might be a little bigger than one at a standard Marriott, but the biggest difference is the room quality (better finishes, materials, etc), plus the soft products (better bedding, bath products, etc) - in addition to any other hotel-specific amenities offered.
By your argument it'd be just fine if a room at the Grand Floridian matched the exact decor of the All-Star Movies resort, so long as it was a bit larger in size.
20-25 years ago, rooms at WDW hotels were on par with industry standards for their similar hotels. Now through resting on their laurels and this terrible homogenization, it is impossible to have a "deluxe" Disney experience.