We are each individuals. I just know what works for me and those I care about.
That said, I would not discount that it works. Motivation only works for me if it is either overwhelming, or I'm in a good space. And that mostly means only when I'm in a good space.
Getting into that good space requires keeping my shoulds only things I want for a long enough time to condition my brain to the idea. This is hard to arrange, takes a good while to start working properly, and is easy to accidentally undo. It certainly isn't something I can just turn on.
I have high motivation/curiosity and struggle hard to do things even if I know like and enjoy them.
Medication helps tremendously with this and I reduced it for a few years and still have behavior patterns I learned on medication