Most of the NeXT folks I worked with left many years ago. Perhaps generous stock options contributed to the exodus. Or perhaps once OS X was clicking along with a new Window Server and graphic sub-system, replete with an Objective-C-based Cocoa API, they felt like the work was complete.

There are nonetheless many of the old guard still there — presumably navigating the Swift-UI transition.

And Craig Federighi is, in my opinion, a very capable captain to be steering the OS ship for Apple.