Inadequate icon on macOS 11 Big Sur (and future)
I would suggest adapting the Firefox icon to the new Big Sur design. Unfortunately, among the most common applications, Firefox is the only one that has still kept the old design (which makes Firefox seem like something out of date and not very obsolete in appearance, while in reality it is a concentrate of care and progress).
The user observes the evolution of an app from the thick icon design, so I can't explain how Firefox can still own its design (which unfortunately doesn't align with the dock). On iOS / iPadOS you have the appropriate icon, why not transfer it directly to macOS Big Sur at this point (thus unifying the interface itself)?
Nothing to say about the rest, you are fabulous and the best (I just suggest a hint of transparency in the panel bar).