A couple of weeks ago, a Chinese developer of FF shared his opinions on a Chinese IT forum concerning the issue of tablet UI. Long story short, Mozilla lacks enough human resources to deal with this issue. As Mozilla is non-profit and many of us are ...
I myself was a FF user. When I got a Samsung Tablet and found that no dedicated tablet UI on FF Android, I submitted feedback on Google Play. Years passed and I still see no improvements, this is why I shifted to Edge as my primary browser on Android...