Maybe I shouldn't have included that second paragraph, since that's not my point. The second paragraph was more of an expression of frustration with how elements of the Apple user base regard macOS as the pinnacle of user interfaces and how everyone places an extremely high importance upon even minor elements.
Then again: while I believe bad UI/UX is a thing, I don't think there is an ideal. Different people think in different terms, or have different preferences. Some forms of interaction are better in one domain than another. There are undoubtedly many other reasons.
As for Firefox taking things into their own hands, that's the developer's decision. I have already given two reasons why that may be the case (users may expect consistency across platforms, and it may require too much effort for too little return).