Not every configuration system is as bad as the m4 nightmare that sendmail used, and I understand nothing really better was feasible in the prelapsarian or Stone Age days of its implementation. But I worked - fought - with sendmail for years and, as in the book, I also remain mildly surprised that Allman continues to perambulate. Most such things in my later professional experience differ by degree, not kind. YAML is not as bad as what was typically perpetrated in Perl days, but it does too much and too little and all its fiddly rules give me headaches. JSON is awful and what we're basically stuck with, because even though it's so simple it's almost useless, at least it's simple. XML is much better than it gets credit for, but nobody likes it because most programmers seem to regard the need to use a keyboard as an imposition, and I assume also have frequent nightmares featuring lots of pointy angle brackets. (I use Emacs because I don't hate myself, and I wish more people had the sense to keep things as simple as Emacs Lisp typically is.)

I don't want to talk about X. Wayland has been about 60% mistakes by volume, and I like too many of the people who made it too well to be anything other than sad about that.