Fixing bugs doesn't require a total redesign (especially not one that blatantly copies another browser that they just so happened to be losing a ton of marketshare to).
As for your screenshots, once you look past the fact that the UI elements are themed differently (ironically, I used to dislike Chrome because it didn't follow the OS's theme closely whereas Firefox did, but now it's the other way around), you see they both have essentially the same layout. Titlebar/pseudo-titlebar on top, tabs next, then the third layer has navigation buttons, an address/search bar (split into 2 in firefox, although mostly unecessary since the address bar can also search), then a bookmark button, and finally a thing that replaces the menubar (which chrome does better). Then it's the page, and at the bottom each browser does not have a status bar, but rather just shows you the URL of a hovered link in a box that pops up when necessary.
Now compare that to an older Firefox, which has: Full title bar on top, real menu bar (which, in older versions was just a normal UI element, in other words you could move it and put other stuff on the same toolbar. Useful for small screens since you could put bookmarks beside it), then navigation toolbar, with a URL bar that wouldn't hide stuff from the user by default, and the search bar. Then it was a tab bar, the page content, and a normal status bar. I think it's perfectly safe to say that Firefox looks more like Chrome than previous versions of Firefox.
Seriously, it can't be that hard to just have a flexible UI where I can put the stuff where I want, and choose what toolbars to show/hide. I know that it's not hard, because they did exactly that years ago. Someone wants the status bar gone? Great, they can disable it. Someone wants tabs on top? I'm sure there's an addon for that.