In classic iOS, when you tapped down on list items or buttons, they’d instantly light up in vibrant color. The standard color was a bright cheerful blue. In iOS 7 through 12, the tapdown state is the color of dirty dishwater.
This is true for many parts of the iOS 7 redesign. Look no further than the default UIKit button. It’s nothing more than just a blue label, that turns grey when you touch it. This boring look of the default UIKit elements is what I think is the cause of the heavy theming of apps and the creation of custom controls. The look of the iOS controls stands in contrast to the richness of the controls in macOS. While you can choose to set all controls to a boring grey (like I did), the default option is a nice blue. You can even choose pink, yellow and green as your contrast color. This is ignoring the nice gradients on toolbars and checkboxes. While I hope, Apple puts some more effort in the default UIKit components, I’m almost afraid they won’t. At least not this year. This means that we’re stuck theming our apps for yet another year.