Rather than wiping out the princess aisle and replacing it with building blocks one might consider the advantage of being a princess.
First and foremost, princesses are pink and sparkly, and what is better than sparkles? Second, princesses, without doing a thing to earn it, are the center of attention. They have lots of power, being the daughters of the kingdom rulers. They don't have to argue, be mean, or even have intelligent discourse to get what they want. They just tell the palace keepers what they want and their wish is granted. Nobody ever tells a princess to "be nice", smile and get along with their siblings. Princesses are adored no matter what expression they have on their face. Everybody loves a princess.
Now if a princess has a magic wand that adds a whole new dimension. Princesses with wands can close their eyes, make a wish and it automatically happens. Everybody has to put up with the princess because the princess has all the power.
So before you simply tell your kid to quit being a princess, you might deeply consider why she is desperate to be a princess. How many times have you insisted that your daughter behave, be nice and be quiet so that everybody(including you) can be impressed with her good behavior?
Would you do that to a son?