Earlier quoted context omitted.
I've heard what you're describing phrase as follows: "If you want to know who truly values you, look for the people who would not be able to replace you with someone else." That usually has us pointing to friends and family, with the odd exception.
I'm not sure this is a reliable guide. I'm in academia, and the people who really can't be replaced are the administrative staff with hard-won institutional knowledge and connections--but they're valued far less than splashy big-name faculty with no institutional loyalty.
While faculty basically no matter how useless can never be fired.
"can't be replaced" has two opposing meanings in your post.