Plus it doesn't offer me as much configurability as Vivaldi, at least in these areas I care for.
I'd love to hear that FF has 50% usage ratę again, but I will stick to chromium based browser.
This is one of the things I love about Firefox. So many options available, even if not "fully supported" tend to work well. Although they appear to be moving away from this approach with the move to only We extensions.
and
> with a CSS rule or two in userChrome.css.
Are firmly at odds. Over 99% of users will not have the ability or the desire to do this. Heck, I know exactly what you mean and how to do it, and I would never do it as it's a pain in the butt. I don't use a browser to mess around with its "conf" files. Either it does what I want or I can change it without leaving the app. Everything else is onerous.