ultimately the support dies out and they die out as well.
Exactly. I've seen multiple, as I'm sure you have as well, just completely lose support. Sometimes someone else will pick it up and take it over, but that usually dies too. ULX and ULib are the only things that have stayed constant in my 6+ years on Garry's Mod.
I'm not saying ULX doesn't need more features, but that is the beauty of it. It is so easy to just add almost anything you want to it with a plugin/mod.