"Swing suffered from two central weaknesses: the tutorials provided by Oracle were... often insufficient. And you could pick up some bad habits by following them. And then there were the UI builders where anybody could draw up something mediocre."

Agreed. Also, the IDEs would typically give you too much rope - enough for a novice to hang himself. When you create a new project with Xcode, you get a default project with all of the essentials for a native app. The menus, a window, an "About" window. Etc. In most java IDEs you get an empty main() method. Making an app that feels like a first-class citizen requires a lot of work and attention to detail.