Mozilla's competition is default apps and chrome which I've only seen advertise on google and youtube, on the random day I use a computer without an ad blocker. Not like Safari is putting out any ads, or that Edge has any fans outside of geriatrics who don't know any better.
The competition (chrome) is just enjoying the runaway success of being the household name for over 10 years, simply by being a better product than firefox was 10 years ago when the market shares were much closer.
If firefox wants to enjoy this runaway success that chrome has, mozilla should steal the playbook of being the contrarian option for tech minded people just like how chrome was the foil to IE and Safari a decade ago before it became the dominant web browser. The focus should therefore be on dev tooling, not marketing, and the rest of the user base will follow the devs.