This doesn't include the latest ESR version of Firefox while the add-on is very likely compatible with it.
It causes Mozilla to deliver old versions to ESR users.
I personally use ESR because I'm not interested in Mozilla's experiments or in downloading a huge update every 6 weeks. Others feel the same or are limited by organisations who can't update Firefox as frequently.
This doesn't include the latest ESR version of Firefox while the add-on is very likely compatible with it. It causes Mozilla to deliver old versions to ESR users. I personally use ESR because I'm not interested in Mozilla's experiments or in downloading a huge update every 6 weeks. Others feel the same or are limited by organisations who can't update Firefox as frequently.