> This approach to careers fails to take into account that we inherently change as people.

OP very much talks about this in the last few paragraphs, both in that you can't plan exactly and that you need to course correct as things change.

Also, just because it's okay or may happen that you change tracks within your career, it's still a good idea to optimize the track you are currently on and have an idea of where you want to be. Just coasting because you can't possibly plan your life seems like a strictly inferior option.