I don't think valuable should be seen as black and white, although companies and employees both make that mistake in different ways.
Irreplaceable is an extreme version of valuable. Companies are right to avoid that extreme. But they shouldn't take it so far that they are allergic to admitting that employees have value. Any current employee who is right in the middle of the bell curve has value because, while they could be replaced, they are a known quantity.
From the employee side, there can be a temptation to believe that because you're not exceptional, you're not valuable. Even if you're merely average, that is OK, and you need to accept that you are a worthwhile member of the team. If mentally you can't claim the position you rightfully deserve as your own, then you believe something wrong about the world, and like any wrong information, that will corrupt your decisions about how to act.
That's the point of companies to de-risk relying on a single person. You can still be a valuable member within your team, among peers, some of which you may even call friends.
Irreplaceable is an extreme version of valuable. Companies are right to avoid that extreme. But they shouldn't take it so far that they are allergic to admitting that employees have value. Any current employee who is right in the middle of the bell curve has value because, while they could be replaced, they are a known quantity.
From the employee side, there can be a temptation to believe that because you're not exceptional, you're not valuable. Even if you're merely average, that is OK, and you need to accept that you are a worthwhile member of the team. If mentally you can't claim the position you rightfully deserve as your own, then you believe something wrong about the world, and like any wrong information, that will corrupt your decisions about how to act.