This post is classic Zach, using nostalgia for respected creations in Disney's history to try to garner support for a modern creative decision of questionable taste.
MK's castle was certainly inspired by the one in the film, but it has never particularly resembled it in any meaningful way. Even in the film itself, the castle has a rather inconsistent appearance depending on the angle, time of day, and lighting shown. And neither are especially literal recreations of Mary Blair's famous concept art that was created during the film's early development.
The current overall paint scheme has no basis in Mary Blair's art, and the decorations that are being added only serve to remove it even further from her style. The piece of publicity art they made is cute and all, but it's rather disingenuous to claim that the park installation has any connection to the original concepts for the film. Multicolored iridescent pastel patterned bunting is nowhere to be found in her gleaming white castle images.
This is just the latest in a growing trend of cherry-picking revered elements from Disney's past as justification for contemporary decisions. It's been going on for years (how many times have they trotted out Walt's quote about Disneyland not being a museum?), but seems to have accelerated significantly in the last couple years, in terms of the frequency that it's being done, the specificity and relative obscurity of the historical elements, and the degree of non-sequiturs it's being used on. Disney has always carefully curated their own history, but the degree to which they're actively re-writing it is concerning.
The more I see of the 50th additions, the more I can't help but wonder if the paint scheme was intentionally chosen to make the castle look like a piece of plastic. The molded fiberglass decorations do nothing to dispel the appearance of being an oversize playset. Whether intentional or not, this looks more convincingly like an oversized version of a real toy than 95% of what's in Toy Story Land.