A mistake that I made too often in life was to focus too much on the specific implementation or realization of a thing instead of learning about the valuable generalizations and abstractions that may be learned from it and applied elsewhere. That was then, this is now.
imenu is actually a nice feature for Emacs. When I learned about it way back when, having quit using the menu bar, I dismissed it as not-helpful. That was a stupid thing for me to do because there ought to be a way to use it with the keyboard. Of course there is.