The author's point is not that there shouldn't be new systems or that no systems should ever change. He's not arguing for a perfect abstraction, either.
Following his development path (AMQP->ZeroMQ->nanomsg + libmill + others) his interest was in decomposing the larger system (AMQP which included message queues, databases for storing messages, wire protocols, etc.) into its smaller parts so that you could build back up to it in a better way. It happens that when you get to those lower levels, you can call them done.
If you're building a web browser, what's the proper scope for your project? Should it actually consist of all of these things in one project: tcp stack, http client, javascript interpreter, html parser and renderer, keyboard drivers, mouse drivers, touch screen drivers, etc.?
No. You build on the existing OS for the drivers. You build on the OS for the TCP stack. You may build an HTTP client, but odds are you can reuse an existing one, or the one you make could be partitioned off into a separate, and hopefully reusable, library. Your javascript interpreter can also be its own project/library. And most of that already exists, so you can focus on HTML parsing and rendering and glue in the other components. Your HTML parser doesn't need to know how to send an HTTP request, your renderer doesn't need to know it either. Only your browser needs to connect the HTML renderer and the HTTP client.