It's truism that one size does not fit all. Yet, there are fads and some people have to re-learn the truism. Here is a summary of U.S. pedestrian malls, showing a mixed record of success.
It's safe to say that the designers of private malls, subject to profit-loss risk, will be less likely to be faddists. If they still are and if they are wrong, they pay the price, as they should.
In a slightly different context, Chairman Mao suggested we let a hundred flowers bloom. But as Paul Romer has taught us, it is all about combinations. Designers are the ones who discover newer and better combinations of elements. Design a chair or design a shopping mall and many more than a hundred outcomes are possible. The combinatorial space is daunting. Inspired designers subject to profit-loss is the only approach that I can think of in light of the scale of the problem.