Sometimes I wonder where Firefox might be today if, in the last 10 years, it had competent leadership singularly focused on delivering the absolute best browser in existence.
HN loved to hate on it's decision but a lot of them (like XUL removal) where strictly necessary for firefox to still have any chance for relevancy.
And while they did try out a lot of things but FF fundamentally has a hard time gaining new users as they have very little killer features. So stuff like pocket, VR or FirefoxOS where needed tries of FF to gain some feature with which you can gain users. Tries they lost but I would say failing to try would have been worse leadership.