I've been using Emacs for a decade and still have never had to write a single package of my own. Every time I have a good idea, someone else has already implemented it.
I donate little bits here and there when I can, but I'm unfortunately not in financial position to give what I think the maintainers deserve. Instead I try to submit documentation patches to projects whenever I find myself digging through the source code trying to answer a question the docs didn't make clear.
I've written a few specialisms that couldn't really be open-sourced. e.g. wiring up inf-ruby and internal dev tools to open up a rails console in dev, or generate a jwt from the auth server in the cluster.
The only package I've been ultimately responsible for is the Gruvbox theme[^1], but that was very quickly handed over to other emacsers :)
I still find it a joy to write and it's one of my more preferred rabbit holes to dive into. Maybe one day there'll be something more to share :)
Oh wow, I used to use that theme. Thanks for making it. Yeah, most of the elisp I write is mostly just glue code, not something that makes sense to package and distribute.