>you have to trust their creators explicitly

Yes, and that same issue stands for extensions that are essential for making the browser usable. Who uses Firefox without uBlock? I won't use a browser that lacks a feature rich vertical tabs solution and that requires me to use sidebery with Firefox. That essentially forces me to trust a host of extension creators that I know nothing about. Yes, source can be reviewed, but I don't have the chops to do it and it doesn't seem like there is a non-profit organization that is taking that on (why doesn't EFF?)