What I learned from that project is that being indispensable sucks. That lesson has recurred in my career either for me, or when I got wiser, for other people.

It's not enough to write reasonable code that 'works' or document it as it is now, there's a whole unmeasured and thus under-encouraged aspect around maintaining a legible edit history. I often am trying to get into the head of the bug author to figure out why they thought this was a feature in order to preserve functionality while fixing bugs. They aren't always around, and they aren't always fun to talk to. If you have the history, the person is free to work on other things. To gift them to people they mentor, or otherwise re-home them. If you don't have that, if it's all in their head, they have to leave to get away from the project.

If I can figure out what you're doing I can figure out how to change one or two conditional blocks to fix a problem. Your code stays intact. If there's no history anyway, and the code is sketchy, I'm far more likely to take the code away from you by rewriting it. We can't have black boxes on the team. That's a ball-hog, and ball-hogs get benched.

If you don't show your work, then you're going to find you have fewer and fewer interesting responsibilities. Because "how we got here" is also a "why" and we ask Why all the time.