'The ghacks user.js is a template, which, as provided, aims (with extensions) to provide as much privacy and enhanced security as possible, and to reduce tracking and fingerprinting as much as possible - while minimizing any loss of functionality and breakage (but it will happen). We aim to *inform* and give you *choices*. No one size fits all, so customize it! And not all sites have the same requirements, so use profiles with custom versions. We won't set you wrong.'
But setting these parameters so that Firefox remains convenient is not easy!