How much does the world need Mozilla? A useful, if uncomfortable, thought experiment is to consider what the world would be like without Mozilla.
Consider the world of Web standards. Microsoft doesn't contribute much to developing new Web features, and neither does Apple these days. Mozilla and Google do. Google, per Blink's own policy (mirroring our own), relies on feedback and implementation by other browser vendors, i.e. usually us. If you take Mozilla out of the equation, it's going to be awfully hard to apply the "two independent implementations" test for new Web features. (Especially since Webkit and Blink still have so much shared heritage.) For example it's hard to see how important stuff like Web Audio, WebGL and WebRTC would have become true multi-vendor standards without us. Without us, most progress would depend on unilateral extensions by individual vendors. That has all the downsides of a single-implementation ecosystem --- a single implementation's bugs become the de-facto standard; the standards process, if there even is one, becomes irrelevant; and even more power accrues to the dominant vendor.
In the bigger picture, it would be dangerous to leave the Web --- and the entire application platform space --- in the hands of three very large US corporations who have few scruples and who each have substantial non-Web interests to protect, including proprietary desktop and mobile platforms. It has always been very important that there be a compelling vendor-neutral platform for people to deploy content and apps on, a platform without gatekeepers and without taxes. The Web is that platform ---- for now. Mozilla is dedicated to preserving and enhancing that, but the other vendors are not.
Mozilla has plenty of faults, and lots of challenges, but our mission is as important as ever ... probably more important, given how computing devices and the Internet penetrate more and more of our lives. More than ever, pursuing our mission is the greatest good I can do with the talents God has given me.