I read that book in the last millenium, I wasn't inclined to go and refresh my memory just to understand your comment.
Re sendmail, when were you working with that? My reaction was just to look at it, say "nope", and used Exim instead. Perhaps the most instructive lesson here is the importance of good choices when it comes to selecting systems to depend on.
Other than that, I'm not sure what the lesson is in "people collectively decided to depend on one of the worst alternatives available." We still see that today with programming languages.
There's nothing really wrong with YAML, except perhaps the way some people use it. I classify that as "skill issue". I work with Kubernetes regularly, and its YAML usage is fine.
Something similar applies to JSON. If it's so terrible, what's better? With JSON Schema and OpenAPI, it's feature-comparable to XML now.
The problem with XML is its completely unnecessary verbosity outweighs its usefulness. I can only assume it was designed by ex-mainframe people who, unlike me, actually yearned for a return to the overengineered environments they were used to. It's no surprise that JSON and YAML edged out XML.
Emacs Lisp is an abomination. Sure, Lisp has its place historically - I had a spirited discussion with John McCarthy about that at a Lisp conference in the 2000s. I'll just mention two words: dynamic scoping. They took decades to even figure out a solution to the funarg problem, and that still didn't really fix the language. Luckily Guy Steele came along and noticed that Church had solved that problem before computers were even invented.
> Re sendmail, when were you working with that?
Oh, only until about 2005. Other options on the table included Postfix and qmail; when I reached a point where burgeoning trust in my engineering judgment coincided with time to replace the oldest production boxes, we commenced to switch to Postfix, primarily because administering that yielded me the lowest Excedrin bill.
Anything with genuine numerical precision would be better than JSON, is what. I appreciate this is an open-ended suggestion with no implementation offered, but if I have to spend one more mortal minute bikeshedding bignum representations in strings, I won't be held responsible for my actions. Indeed just the thought reminds me part of my purpose in this time apart from labor is to decide whether indeed I will train as a lawyer, where I understand time similarly spent is billable in six-minute increments.
I wish I'd been a fly on the wall for your discussion with McCarthy, as perhaps I also wish you could have been for a very spirited chat I had with Stallman around 2016 on the merits and externalities of his and FSF's philosophical approach. I appreciate you taking the time of such a detailed and thoughtful reply, which I confide I'll later revisit and find benefit beyond that already apparent. Enjoy your day!