In my opinion the new GM UI is too big and in your face, taking up the entire screen.
As shown here --> https://prnt.sc/wWmSVi-VhpB4

Compared to...

Arma 3 Zeus --> https://prnt.sc/QNoiTILAw_n3

Its a lot easier on the eyes and to navigate. Plus if something is happening to your players and you need to intervene asap you cannot see behind the Reforger GM UI.