I agree with absolutely everything you said. Mozilla’s development processes are just insane. “Change for the sake of change” should be their motto. The insistent need to copy what other browsers are doing (or more accurately, what they’re not doing) is absolutely maddening.
Honestly, for me, version 3 was where Firefox hit its peak. The layout and GUI was almost entirely customisable. Version numbers weren’t rocketing up by factors of 100 every 3 weeks.
Then the race to keep up with Chrome’s equally stupid version numbers began, and so did Firefox’s fall from grace. Features changed and disappeared. I remember an update where they just totally reassigned a frequently-used hotkey (Ctrl+E or Ctrl+L, if I remember correctly) to a completely different function entirely. So anyone who’d been using that hotkey for years (like me) just had to “deal with it” (it was eventually changed back, by some god-sent miracle of common sense).
If that isn’t a middle finger to the user, I don’t know what is.
Now the obsession with minimalism and getting rid of modal/dialog windows and shoe-horning as much useless semi-spyware crap as possible into the browser (see: Pocket, Experiments, etc.) has gone beyond all reason.
And let’s not even mention the loss of the ENTIRE extension ecosystem when changing to Quantum. How many hundreds of thousands of man hours were flushed down the toilet in favour of crippled functionality which has not even remotely begun to catch up with the ability of old extensions?
As a developer, losing Firebug is something I still lament on a daily basis. Sometimes I actually use a version of Firefox 40 just so I can still use Firebug, because Firefox Developer Tools simply sucks balls (you can’t even resize the width of the columns in its GUI, FFS!)
I yearn for a return to the “good old days” where browsers were actually controlled by their users and not the other way around.