It's been unmaintained for years. The developer moved on to uBlock Origin. You should too.
Has anyone tried this extension?
I'm using it, if site breaks I usually check which calls it makes on extension UI and lower protection for that API (if it makes sense).
It is suggested by FSF, but not sure why it is not more popular
I mean my understating is by adding more extensions to your browser you are more vulnerable to vulnerabilities.
What's wrong with uMatrix?
It's been unmaintained for years. The developer moved on to uBlock Origin. You should too.