I think he covers this early on: if you don't aspire for anything more, congrats. Incidentally I'm in the same boat. Literally told my manager "nope, not really interested in pursuing a promotion. Just want to be paid fairly and continue working at this level." They actually appreciated having one less engineer that they have to try to cultivate a career for.

Not following a strict career plan does not mean you aren't aspiring for growth. In fact it may be the exact opposite. Being loyal and jumping through hoops for your current team/manager/company in the hopes of a promotion may mean that you are ignoring other opportunities out there that may be a much better fit for you. Your company's career ladder is designed to get you to stay there for as long as possible while minimizing compensation. It does not prioritize your personal growth over the company's. Especially in today's world, the people most likely to get ahead in life are ones who stay flexible and ready to jump on new opportunities as they arise.