I've used arkenfox's firefox user profile for a good amount of time now and you're right to have some doubts about it.

No mitigation measures are foolproof and in actuality may result in you becoming more identifiable if you apply it improperly. The irony is that you're less likely to be identifiable using default settings on a default firefox instance than say enabling fingerprint resisting + ublock etc.

Privacy in the context of online browsing is achieved through obscurity. It uses techniques applied by browsers like TOR to become effective. In the case of TOR a wide adoption and it's careful implementation has made it one if not the only browser I would say offers decent privacy by default. In our case this template's usage is just a pretty insignificant fraction of the internet.

Browser fingerprinting technology is constantly evolving and uses many metrics that you may be unable to address if you're one to seek privacy. Just take it with a grain of salt. Although things may not look good for browsers nowadays. I'd say some privacy is better than no privacy at all.