become rigid or fixed
ossify - stiffen
The original and technical meaning of the word ‘ossify’ is ‘to become bony'. It has since been adapted for use in a formal and disapproving way to refer to something, such as ideas, habits, or behaviour, that becomes fixed and therefore difficult or reluctant to change. Outside of the field of medicine, it is in the latter sense that the term is most commonly used.
The CEO’s early success only served to ossify her thinking. It made her believe that that approach was the only viable method of achieving success.
The ossification of the political party means that they are out of touch with younger voters. They must find a way to modernize before the next election.
I believe that the entire institution is ossified and archaic. It needs revamping from top to bottom.