I think JWZ's talking about unnecessary abstraction layers, and re-written wheels created by technology fetishists and bad designers, rather than lamenting the lack of knowledge required to make useful things in modern OSs.
Yes, but which abstraction layer in the WebOS is unnecessary? I think I disagree with JWZ on this one. Is it really better to have for instance all the formating capabilities of CSS built into the Desktop-OS' native widget set? Than you would have to coordinate your OS development with the development of the CSS specifications.
Rather than having one specification for layer in web apps, and another for local apps (eg, iPhone or Android), there's a single layer. It's very DRY.