We have already been moving towards this approach for quite some time, even though the author doesn't mention this. If you are going to build a web app or API today, do you just start writing code wily nily? No, of course not. You look for frameworks and proven/established ways of doing this. We're practical, we don't want to re-invent the wheel (unless its a side project).
I've recently built an event based API for a client, and much of the work is not "writing code", but figuring out the right tools for the job, based on the requirements of how I believe the tool should work. A lot of it is plugging in frameworks and tools that already exist (and are established), which mitigates (but doesn't solve completely) the question of using complex/untested code. For example, most people use take advantage of TCP or HTTP for a web app. Do we test that low level code? Of course not... its already the most tested code in the world.
I think there is a danger in writing a lot of "custom code" as I like to call it, because then you really are introducing brand new functionality, that potentially has never been tested before. You can and should test your code, but often that will fall short, because you (or your team) cannot possibly test every imaginable scenario the code will face.
My general belief is this: the programming of the future won't involve much programming at all, it will be more like "system architecture", where you pick and choose the tools to meet your requirements. In the world of open source and AWS -- all the building blocks are there, but its your job to figure out how to put them together.