Agree with everything except the "people don't change" point.
People are constantly changing, but they do for so little and so slowly that we don't see it immediately. It's a long term thing that works in many little ways. For some things we change for the better. For others we change for the worse.
But it's always little by little everyday and depends on the world that surrounds you and how you interact with it.

What it's wrong is expecting you or your partner to change in one day (or month, or even a year).