There are people like yourself who would be happy to donate, but not nearly enough. Replacing MoCo's current revenue with donors would require donations at the level of Doctors without Borders, American Cancer Society, or the Make-a-Wish Foundation.
Turning into one of the largest charities in America overnight simply isn't realistic. A drastic downsizing to subsist on donor revenue also isn't wise when Mozilla already has to compete with a smaller team. And "Ladybird does it" isn't a real argument until and unless it graduates from cool project to usable and competitive browser.