As an example: https://ibb.co/Wynn5Tg
Subjectively(!) Firefox is cluttered and takes much more space than Chrome for itself. Unfocused tabs are hard for me to make out on Firefox.
I think that personally I'm a lost cause. Either give me Firefox in a Chrome's pelt or I stay with Chrome. And maybe that's good this way: Firefox should just focus on new users and make the best browser for "them".