I don't work for Mozilla but presumably they will be at a disadvantage in identifying and thus prioritizing features that their customers want compared to competing browsers. Less features -> less users -> less revenue from google for paying to be the default search engine which then completes the reinforcement cycle as they will have less money to spend on features.
Now they probably don't NEED it, but with every user they lose to chrome, they get less and less money until the only market for them would potentially be the privacy focused ones (although I here chromes got really good privacy features nowadays) which are such a small population that they wouldn't even have enough customers to justify the revenue to even match competing browser features. Thus, you would end up with a lackluster browser that cannot match competing browsers and its only niche are privacy people.
Now they probably don't NEED it, but with every user they lose to chrome, they get less and less money until the only market for them would potentially be the privacy focused ones (although I here chromes got really good privacy features nowadays) which are such a small population that they wouldn't even have enough customers to justify the revenue to even match competing browser features. Thus, you would end up with a lackluster browser that cannot match competing browsers and its only niche are privacy people.