https://elm.dmy.fr/ (and https://dark.elm.dmy.fr/, see here for context) sort packages by actual usage in other packages and open source elm applications on GitHub.
The same ranking is used in elm-language-server.
I have not updated the ranking since 6 months ago, but it should still be quite relevant for mature packages. I will likely update it again in the coming months.
Edit: the ranking is an experiment and an evolution of the one described here.