It was never so black and white. If we define control as the ability to configure the browser as one wants and its extensibility then I'd agree that Firefox did

It was never so black and white. If we define control as the ability to configure the browser as one wants and its extensibility then I'd agree that Firefox did have far more control until the Quantum update where it was gutted, while some Chromium based browsers like Vivaldi are feature rich and have features Firefox doesn't (only now approaching a quasi-equivalence with the pre-Chromium Opera before it too was gutted). I still no longer use Firefox as a main desktop browser due to the features I loved no longer being possible and never getting equivalents, despite using Firefox as a mobile browser and every other day on desktop for other purposes. However due to the Manifest v2 phase out some of the more useful extensibility on the Chromium side is being removed (outside of say backporting like Brave but we'll see how long that will last), so one may have to consider alternatives if need be.