Lack of styling in terms of color and fonts is generally not a problem, but it is true that Apple limits more advanced styling for many standard UI components.

Lack of styling in terms of color and fonts is generally not a problem, but it is true that Apple limits more advanced styling for many standard UI components. For example iOS navigation bars (as in UINavigationBar) are not very customisable. If one wants to customise the look entirely, for example make the bar taller than the standard 44pt, one has to implement the component from scratch. My perception is that the limited customisability is done on purpose by Apple to enforce a common look-and-feel of UI elements across all apps on the system. Also it of course reduces the API surface that Apple have to maintain. I pretty much like it, both because it indeeds lead to a more consistent look and feel, but also because makes it easier for us to reject the weirdest design wishes from our clients - we can refer to that implementing the components from scratch will take a lot of time (= money).