So do I. There are things like text replacement, download progress indication on file icons, and other Cocoa-esque things that don't work on Firefox, but outside a probably very small segment of users who would even notice these things, and a smaller yet segment who would actually care, Firefox feels at home enough in macOS.
What I think damages Firefox's user-friendliness more is how easy it is to get to setting screens that look scary to the average user. For example Firefox recently started recommending an extension called "Enhancer for YouTube" when a user visits YouTube after upgrading to some new version of Firefox. Upon installing the extension, you get taken to the extension's settings screen which has a design that would definitely throw off my non-techie family members [1]. Also, take a look at the Firefox release notes for iOS [2] – sure it's "nice" for us devs to have access to raw GitHub issue labels or whatever those are – but for non-techie users they might be interpreted as conveying a certain messaging that Firefox is not really designed for them.
What I think damages Firefox's user-friendliness more is how easy it is to get to setting screens that look scary to the average user. For example Firefox recently started recommending an extension called "Enhancer for YouTube" when a user visits YouTube after upgrading to some new version of Firefox. Upon installing the extension, you get taken to the extension's settings screen which has a design that would definitely throw off my non-techie family members [1]. Also, take a look at the Firefox release notes for iOS [2] – sure it's "nice" for us devs to have access to raw GitHub issue labels or whatever those are – but for non-techie users they might be interpreted as conveying a certain messaging that Firefox is not really designed for them.
[1] https://i.imgur.com/8TIetRA.png [2] https://i.imgur.com/QoUG1ZF.png