I feel like your last sentence fails to acknowledge the conditions that a lot of UI designers are often just one in a line of cooks.

A great deal of UI designers aren't given the leeway or opportunity to make profound impacts on their particular projects for reasons including limitations of: engineering manpower, data, time, budget, or corporate willingness.

I wouldn't be surprised if most of the time, the majority of UI designers are given project criteria LONG after a lot of things about the project have been set in stone, including if the solution for a particular problem should even be a UI in a device!

The city planner you are thinking of is often a Director/Chief of Product (if an organization even has one) or CCO, not strictly a UI Designer.

Yes I think you've said it better than me. So many designers are devolving into decorating interfaces instead of designing new products. To be fair, many of them were never truly up to the task, but then I suppose we need a new nomenclature for Product Designers vs Interface layout specialists.