Disneyland has more repeat regional visitors and nostalgic promotions like that will draw more people in, just for that occasion.
Could work at Disneyworld as well, but most would be making the trip with or without the promotion.
The "90's" could also be a "before I was born" event for a greater percentage of DisneyWorld visitors. Even if "mom and dad" were interested, it would be lost on the kids.
That plus also you have people who complain about the parks closing early and not getting a full day at the park. Several years ago in the spring they used to run what they called the Pirate and Princess parties on the same schedule as they would run the Hallowe'en and Christmas parties.