Firefox is a well known browser. People just don't use it because Chrome offers something else. Firefox has always been a "Chrome lite", following in their footsteps instead of standing on it's own terms.
They abandoned their privacy direction, only coming back when it's beneficial for them to market it. While Chrome sucks for adding features that aren't standard, Firefox needs to just be quick with it too. It took Firefox forever to add tab groups, something people were asking for all the time.
They are absolutely out of touch with their user base and have no direction. Opera GX targeted the gaming niche and now they have similar market share to Firefox, which is insane. It's a shit browser, but at least they went for something. Firefox just idles and adds whatever is popular way too late. Nobody wanted AI shit added, why was any development time wasted on it? The engineer is right.