It used to be EXTREMELY personalized and personalizable, right out of the box, even without extensions. Mozilla has systematically REMOVED FUNCTIONALITY from the browser, and I'm not talking about switching from XUL. Personally I don't care if XUL ever comes back. I don't even use many extensions, mostly just uBlock.
A couple of versions ago they took out right-click for image properties! a basic function of browsing since Netscape Navigator and didn't add it back until two more releases. They took away my compact view mode. They foisted less powerful menus on me and removed configurable settings from about:config, the single most powerful customization feature of the core browser.
They keep chasing a new Chrome-like feature or look while killing things I use regularly. I don't want that shit. I want the old customizable feature-rich Firefox experience I had back in the 2.0 days.
So many users eject after each interface overhaul or silent removal of basic functionality and Firefox's trademark customizability. Yet they kept doing it. Madness.