This critique sounds like it comes from someone who has engaged with a wide range of topics enough to know that there is a lot of detail and nuance, but not enough for any of it to have coalesced into a simple understanding of it.
Cage's music is annoying and pretentious, and I largely think that because Cage was annoying and pretentious. He made a classic mistake in the art world of trying to tell people what his work was about and then getting pissed off when people either still didn't like it or chose to interpret it differently. That's a rookie mistake, and it's a fight artists never win. The smart ones keep their mouths shut and let the work speak for itself. The good ones make art that can be meaningful to a lot of different people in a lot of different ways. This was one of the great sticking points in the "War of the Romantics" between the New German School (Wagner and Liszt) on the side of program music against the Leipzig group (Schumann, Brahms) pushing absolute music. This battle between composers arguing about whether meaning should be explicit and imposed or if it should be intrinsic to the music and left to the listener was the context for Cage's work.
And his work is most charitably interpreted as social commentary, even though that's not what he wanted. The best thing you can say about it is that it asks the question, "What is music now?" But he thought he was the first person to ever ask this question and got really irritated when people pointed out that academics had been asking this question for a couple thousand years. So, a lot of very serious musicians thought he was pretty dumb, and he got pissed and said it's not dumb, you're dumb and you don't understand it, and if you were smart you would think it's all genius. It's really hard to defend that kind of a person, but it gets easier as time passes and you can stop thinking about the artist as a person and think of the art. But as a professional violinist for over 30 years and a music theorist, I don't object to the Hof's assessment. I could say similar things about Milton Babbit too, integrated serialism, and a lot of contemporary classical music. It would probably get a response from a certain kind of person who would say that I just don't get it or that I haven't given it proper study. Well, I have, and I think it's kind of dumb, it's been done before, and I no longer have the youthful zeal it takes to debate these things point-by-point.
Similarly, the criticism of the treatment of Zen also seems a little youthful. I grew up in a very Catholic family with parents who basically don't accept Vatican 2, and still practice Latin mass, and a large part of my home schooling was the intense study of Catholic history, philosophy, and theology. I took being Catholic extremely seriously for a very long time. But over the years I came to the conclusion that it was basically a bunch of cute fairy tale stories. Wonderful philosophy; terrible religion. And I'm not blind to the rich cultural heritage the Catholic church is responsible for. As a classical musician, I'm extremely aware of (and grateful for) how much the Church is responsible for Western Music as we know it today.
As I was drifting away from Catholicism, I got pretty deep into Buddhism. Ultimately I came to a similar conclusion. Great philosophy; silly religion.
Ultimately this article comes across almost as whiny and angsty and teenagery as John Cage does when he's defending his music: "You just don't understand me!!!"
No dude. Trust me. I understand it. It's just kind of stupid. You'll grow out of it eventually.
The book isn't perfect by any means. It is contrived. I don't think you could write a book like that today. But it was written in a very different time. A time when the knowledge divide between ivory tower academics and lay people was explicitly desired by the academics in a wide variety of fields, including--classical music. Babbit was famous for arguing that classical music should not be comprehensible to anyone who didn't have a PhD in Music Theory or Composition. That classical music deserved to be as respected and obtuse as advanced math and science, and that normal people didn't deserve to be able to understand great art. This book was a direct reaction to that academic pretense, and it presaged an era that has disseminated more knowledge across a wider range than any other explosion of knowledge since the printing press--and far outdone it.
Outside of that context, the book almost doesn't make any sense. Why would anyone write like this in a world where the top academic minds of every field lay out their innermost thoughts about the most challenging problems in their field on their blogs and talk to riff-raff in the comments and try to make things as understandable as possible? Well, no one writes like that any more. Not even Hofstadter writes like that any more. It is an artifact of its time . . . a lingering remnant of a world where knowledge had to be protecting by intellectual elites and a wide-ranging understanding of difficult concepts was seen as a threat to the academic establishment, and a reminder of how recently things worked that way.
When I was a kid violinist just getting into the completely new world of these concepts, it was illuminating and perhaps life-changing. As a grown up now with a different perspective, I can't see how it would have nearly as much of an impact on a younger person in today's context, and so in my world, its value has shifted from being the kind of book that initially illuminates a certain set of ideas and now reminds us of the world we came from way more recently than it feels like.