I'm not quite sure anyone realizes what it takes to maintain a small project like this and keep it up to date in line with a project from an organization with paid employees like Firefox & Mozilla -- especially considering how many changes Firefox has seen in recent months.
https://www.ghacks.net/2017/03/07/cyberfox-proclaims-death-of-web-browser/
Even the ESR branch offers no guarantee of stability:
Which leads me to wonder how many people use IceCat versus how many that actually contribute to the project?