The first? Newer display technology and processing power, allowed for more complex menus, decision trees, and visual effects/feedback.
The second? Computing was new, and we were still learning how to build basic, usable UIs.
Yet ever UI change distracts, causes lag for users, and the above two points are long factored in.
No one needs a fork to change. No one needs their remote control's volume button to change.
Worse, no one need it to change from one day to the next, on a weekly or even yearly basis.
Many users would be beyond overjoyed, if their browser UI didn't change for the rest of their life.
The back button doesn't need to move, become something else, leap from the top to bottom of the window, look wildly different as a default, behave differently.
Worse, almost every UI change I've seen in Firefox in the last decade, has been tiny little tweaks without any real value for the end user, yet alienated people.
And worse, forced on people. Way to keep market share.
Firefox could be #1 again, simply by firing every UI person, hiring developers with that cash, and just optimise, merge in new web standards (without creating or taking part in them), and fix bugs.
I think that is the wrong end of the stick. People complain about Firefox not because they hate it. They complain because they care. It is the same thing with Apple or in fact any other brands. They want it to be better, they want to come back or keep using Firefox. And they want more people to use it ( for one reason or another ).
So the saying good there is no such thing as bad publicity. Firefox still getting the upvote to front page or being complained is a good sign many user or potential user still give a damn.
I still love Firefox, I just dislike Mozilla's management.
More to the point, the stakes are really high for FF now.
I use and love FF, but FF's market share is very low and shrinking. If they can't do anything to turn that trend around, web developers will ignore it, and it will become useless for many sites.
FF users have to wish/hope that FF rights this ship, and that means they can't afford to lose any more users (and really, that they must somehow reverse course and acquire new users). So every update feels really important - the shrinking user base is an existential threat to the browser.
Haters gonna hate, that’s just how it is.