Except plenty of stuff has changed since NeXT days.
Objective-C driver kit no longer exists, its C++ replacement is on its way out, being replaced by a userspace version.
The watch uses watchOS UI KIT, is isn't either UI Kit nor Cocoa, so three generations apart from NeXTSTEP UI framework, which is anyway being replaced by SwiftUI.
watchOS uses a customized version of bitcode as deployment format, which is now being transitioned to actual native code in upcoming versions.
Related to Doom, watchOS doesn't do OpenGL, or NIB files from Project Builder.
Objective-C driver kit no longer exists, its C++ replacement is on its way out, being replaced by a userspace version.
The watch uses watchOS UI KIT, is isn't either UI Kit nor Cocoa, so three generations apart from NeXTSTEP UI framework, which is anyway being replaced by SwiftUI.
watchOS uses a customized version of bitcode as deployment format, which is now being transitioned to actual native code in upcoming versions.
Related to Doom, watchOS doesn't do OpenGL, or NIB files from Project Builder.
So almost nothing like NeXTSTEP.