I've noticed that the longer your career is, the harder it is to find someone who can replace you. E.g. if a company wants you because you grew MS Office for 5

I've noticed that the longer your career is, the harder it is to find someone who can replace you. E.g. if a company wants you because you grew MS Office for 5 years and then did the same for Google Sheets, and they want you to help them do the same, there are few substitutes.