The first two paragraphs of the the OP’s book-excerpt, above, are the subject of occasional debate on this forum. I am guessing that Percy Goetschius would argue that knowing music theory is a good thing.

I’m guessing few on this forum would argue with the following: Machines have a learning curve, that the process of mastering them can interrupt creativity, we need to practice on our machines to avoid sucking at them, that we may have to stop and read the manual, that knowing about our gear is desirable, etc.

Replace machines with music theory and suddenly people are offering sacrifices to the gods of intuition to ward off evil spirits.