> the change would have involved fixing hundreds of thousands of pages

Even if these pages are static files (although any site opetating at that scale should have some kind of page-generation system), this still sounds like it could be resolved with a simple find-replace using <insert your favorite text editor>.

EasyList is definitely in the right here. Adding an exception results in an unnecessary performance penalty and creates more complexity for the project. Both of these impacts are small, but they can't afford to accommodate for every website like that.

If they want their users to use their site, they should make it work on their user's environments. I doubt they would demand Google or Mozilla accommodate for them like that.