Mozilla have done a huge amount lately to alienate a lot of their long time users, and this is another of the reasons for their steadily declining market share. Numerous decisions such as to push the awful Australis makeover, constantly strip out more and more customisability, bundling Pocket, and the impending ditching of their powerful addon ecosystem are all decisions which have helped to drive people away from the browser - whilst failing to draw new users to it.
I agree that Firefox can flourish without being the most popular browser, but Mozilla needs to start focusing on what their users want and how to carve out a niche in the browser market, rather than pushing one dumb decision after another onto their user base whilst turning Firefox more and more into a simple clone of Chrome. Once Firefox 57 lands, it'll just be a browser that looks like Chrome and uses lightweight addons like Chrome .
For the record, I ditched Firefox around 3 years ago after the Australis turd landed and have been a happy Pale Moon user since.