IMO if they want to be slightly different Chrome, they should just take a full leap and cut out the functionality not used by or confusing to the users they're trying to target. Drop the pretense of control or customization. They're only hurting themselves in the long run by trying to slowly drag one userbase into the other and satisfying both poorly as a result.
there are some about:config tweaks to change the url bar back to the old one, but they are going to go away for sure.
But perhaps you meant FF was heavily extensible which is true, but it was also very costly.
In my opinion, Mozilla should put the vast majority of their energy and resources towards targeting power users and developers - they've already lost the other battle.
Btw, you aren't a browser power user just because you use ctrl-L to focus the url bar. HNers like to think they're power users because they think their opinion matters the most, but it doesn't make much sense when it comes to web browsers imo.
(I like the new url bar, and I'm a power user if there's such a thing)
Also FF/Mozilla cannot survive on power users & developers alone.
By the way, what even is a power user on the web?