I hate to sound too crass here, but Walt is dead. We all have a certain respect for the man around here, but he's not calling the shots anymore.
We also have no idea what he'd think about the state of Disneyland today because he's not here to say anything. We can quote him all we want, point out concept art from the 1950s, but we have no idea how his opinions and decisions would have changed over the years. None of us here can speak for him. And who knows what the company would be like today if he was still alive. We can all fantasize, but none of us know for sure.
Also, the castle was built before Sleeping Beauty was released. Initially, it was to be named after Snow White. This is what her castle looked like in the film, and doesn't look like the Disneyland version at all. (And I just noticed - the Beast's castle is really a more fanciful version of this.)
Walt made the switch eventually because the company had poured a lot of time and nearly a decade into production for Sleeping Beauty - he wanted to do some marketing/synergy. The actual physical design is based on this real castle, but never based off of its color scheme.
The films never dictated the structural design, which was lucky considering the switch. But the castle was always intended by Walt to be not only an icon, but a vessel for marketing.