Mozilla should reinvent the browser again. Browser is what makes Mozilla. If they don't clean it up it wont be successful anywhere else. If they make it work it will span into other areas like IoT, mobile phones, cars... naturally by people willing to use it for their projects.
Trying to push broken/sluggish/buggy software beast into those areas using heavy investments of resources that Mozilla needs elsewhere is management's misstep.
I am the user of this browser since Phoenix 0.5 (not to mention Netscape before). But it is lately that I started slow migration to Chrome. It all started with inability to use debug tools properly (not working, misleading debugger, extremely slow responses) then terrible video performance on Youtube and crashes and UI freezes... The only reason I use FF on Android is because it supports extensions.
It is sad to hear something like this from myself - me, die-hard Firefox fan.