Mozilla Corporation has been growing -- I think it's around ~700 paid folks right now -- but that's still very, very small compared to the number of people employed by its peer organizations at Apple, Microsoft, and Google.
But that's irrelevant, because the Mozilla project, emphatically, is not the Corporation. Mozilla didn't change the world by having the most money, or hiring the most engineers. It changed the world through the contributions of the world. By being born of the open source movement, and recognizing the potential of an open web. Insofar as Mozilla exists at all, it exists to support you, and the open web. Consider getting involved: https://www.mozilla.org/en-US/contribute/