Comment by II2II

Most of those are subjective details and vary from platform to platform. Fine adjustments for each platform isn't guaranteed to attract many people to Firefox either. After all, the UI/UX of Firefox is good even if it isn't excellent. Factors such as convenience (e.g. familiarity or being pre-installed) are likely bigger factors. That said, I will grant you that things like the visibility of the find bar is poor.

It is also worth noting that the macOS UI/UX isn't anywhere near perfect. It is a hodgepodge of design decisions that go back to the origin of OS X or, in a few cases, the origin of the Macintosh iitself. Padding and margins may help achieve visual balance, but it's Windows management paradigm is an absolute functional mess.