I don't think that Mozilla employees must read every single addon. Automated security check is not a reason to state that extensions are useless.

Many 'unmonitored' extensions are useful. There is an article to help with assessment. https://support.mozilla.org/kb/tips-assessing-safety-extension

Firefox warnings appear on almost every extension page. A warning from Mozilla on the few extensions i want is in fact a legal disclaimer by Mozilla that it is, in auction parlance "sold as is" in other words, its up to the buyer to examine the object, provenance etc. but we are not engineers, at least i'm not. and to take the time to learn developer codes etc. is not what i signed on for.

Based on this, i won't be using extensions other than the ones I trust for years. Mozilla's "recommendation list" is scant.