Despite the general level of incompetence among GM's leadership there were a few smart people there. Lutz was one of them. He has a strong track record of developing successful products and has never been shy about criticizing his bosses.

And to get to his point, it's fluff

It's not fluff. Perhaps this synopsis of his book didn't provide sufficient detail, but his point is broadly acknowledged as one of the major problems with the US auto industry. If you look at a US made car from the early 2000's, the level of cost optimization at the expense of all other factors is embarrassing. It's indisputable that as MBAs have gained prominence in the US auto industry, the products have become less compelling. Lutz is simply advocating that the people who love the product be the ones who have the final say.

(Disclosure: I'm an automotive engineer)