If they honestly wanted to add functionality, the Firefox developers could do it in a way that didn't disrupt existing users. Apple did this more or less right with Spaces, Expose, and the Dashboard - I don't use any of them, I never will, and I don't have to to perform the same basic tasks I've been using a Mac for since the 90s. The shortcuts are on the keyboard and in the system preferences but it's difficult to accidentally invoke these things unless you're looking for them. They're unobtrusive.
The frequent buzzwordy trendy chrome-chasing "disruption" designed to draw attention to the changes is one of the reasons I left Firefox - I don't need my browser to "reinvent" itself at random. That happens enough with iTunes, thank you. I need it to get faster, run the add-ons I want, and otherwise not change at all. Firefox isn't really a browser anymore, it's a UX playground with a captive audience that's slowly trickling away to browsers that don't change their core functionality as much, or as often.
Chrome recently tried to push graphical bookmarks on me - an under-handed and unannounced violation of trust that gave me a panic attack. Fortunately the change was easily reverted, but it was a harsh reminder that no browser is safe - developers drunk on kool-aid can and will change whatever they want whenever they want it doesn't matter how strenuously users object or how well-reasoned our arguments are, we're always dismissed as "edge cases" or brushed off with a dismissive "nobody uses a browser that way."