[snip]
Firefox developers have decreed that their users are too stupid
to cope with an "on/off" switch for Javascript. Sad, but true.
In the last decade or so, the overall Firefox policy seems to have become
"forget whatever we used to do, let's force people to write extensions
to provide those features". And in the last year or two, as people
started using extensions to provide the features Firefox has stripped
out, the policy has become "let's block the use of extensions".
https://support.mozilla.org/en-US/kb/add-on-signing-in-firefox
So, uh, good luck.