I actually don’t agree, and the reason is - non tech people. You and me can install plugins but ordinary people don’t do that. So the default experience must be good, offering improvements to the experience over Google Chrome.
Otherwise all privacy features could also be plugins. Imagine if that was true. Firefox would have no identity and you would have to install plugins and make it your own.
So some features should be built in. Maybe the ability to get pop-ups about false reviews will actually make users go “wow that is so useful”.