I'm all for trying to understand what one is doing (and I wholeheartedly agree with TFA's point), but the reality is that very few people in the world really understand all intricacies of one's operating system.
One of the problems (as I tried to argue) is that most Unices have become far more complex. The question is if the extra complexity is warranted on a server system, especially if bare Unix (OpenBSD serves as a good example here) was not that hard to understand.
Of course, that doesn't necessarily mean that we should look back. Another possibility would be to deploy services as unikernels (see Mirage OS) that use a small, thin, well-understood library layer on top of e.g. Xen, so that there isn't really an exploitable operating system underneath.
One of the problems (as I tried to argue) is that most Unices have become far more complex. The question is if the extra complexity is warranted on a server system, especially if bare Unix (OpenBSD serves as a good example here) was not that hard to understand.
Of course, that doesn't necessarily mean that we should look back. Another possibility would be to deploy services as unikernels (see Mirage OS) that use a small, thin, well-understood library layer on top of e.g. Xen, so that there isn't really an exploitable operating system underneath.