If it takes this many people to make a browser then maybe web standards are more complicated than they need to be. This suggests that there might be some big refactorings and restructuring of the web coming in future.
As useful as Mozilla might be their business model is skating on wafer thin ice. They rely on money from Google, and it's not clear to me that advertising is going to remain the cash cow that built their megacorporation.
Maybe browsers just aren't sustainable and the "everything in a browser" idea will eventually go away. We already see that partially with apps on mobile.
@bob Qualifying that - I think it depends on what you want the web to do, to some extent. There are people who want to turn the browser into a platform-independent thingy to run "desktop" apps e.g. electronjs. Putting aside whether or not that's a good idea (and for the record I think there are better way of doing it), you need all sorts of shit to support such stuff which has little to do with the web as a means of disseminating information. (A better solution to cross-platform was things like Delphi IMO - not that I've ever used myself it but a programmer I well respect was an enthusiast)
@maiyannah If Google didn't want them to exist they could probably kill the company just by withdrawing finding. Mozilla's financial statement says their income is from supplying information as negotiated with search engines and I bet that's going to be 90% Google.