In most companies, it's good to let you leave, if they need 5-10 people to replace you. You take this as a point of pride, but I see folks like this as organizational bottlenecks.
When I leave an organization, my goal is for them to either directly replace me, or for them to not need to replace me at all. I do this by ensuring that I don't silo my work (by ensuring others are working with me, or under me), documenting everything I work on, and occasionally changing roles.
My specific goal is to help a company grow, not to make them depend on me.
I'm prioritizing myself. My value isn't based on how dependent people are on me, it's based on how well I scale the company. They could fire me whenever they wanted and the business would continue running, but they don't want to fire me, because my value is high. My approach has landed me consistent promos, raises, and out of band stock grants.
If you think you're safe because the company is so dependent on you, you're misguided. You're the kind of folks that are actively targeted.
Ignoring money, I'm also prioritizing myself, because by removing myself as a dependency, I also make it possible to take vacations, and my stress levels are low.
You think you're making yourself indispensable by making the company dependent on you, but you're doing the opposite. You're a bottleneck, and when companies are trying to become more efficient, you'll be top of the list to make disposable.
Growth is understanding that you become indispensable by removing yourself as a dependency, because you uplift everyone around you. At higher levels of seniority, this is what orgs actually care about.
When I leave an organization, my goal is for them to either directly replace me, or for them to not need to replace me at all. I do this by ensuring that I don't silo my work (by ensuring others are working with me, or under me), documenting everything I work on, and occasionally changing roles.
My specific goal is to help a company grow, not to make them depend on me.