IMO the whole "metaphysics of quality" thing needs to be taken with a huge grain of salt. As you find out later in the book, he actually was diagnosed as schizophrenic (and went through electroshock therapy as a result), and it becomes pretty clear throughout the book that his whole thesis doesn't actually make any sense, and is more the ramblings of an insane person.

There's a few insights to be taken from the book but I largely agree with you that after reading it a few times, it's not worth the praise that it gets.