Odd criticism.

UIKit is the iOS counterpart to MacOS’s AppKit and both are implemented as convenience wrappers around CALayers. They are also infinitely customizable. You can overload UI/NSView and draw vector-pen style on a blank canvas or render whatever you want on a GPU frame buffer. This is how MapKit, Safari, and the Camera view is implemented.

Not sure what you mean by "implemented as convenience wrappers around CALayers," especially when it comes to NSView where you have to opt-in to layer-backing.

It’s a criticism from recent experience trying to build AppKit based UI. The examples you list barely use the stock widgets.

There’s decades of accumulated cruft in Cocoa that Apple discarded when implementing iOS.