I do hope that optimisation is still possible but say when I set land detail on low or even medium landscape already looks very low-res beyond the high detail square surrounding the aircraft.
Bohemia Interactive is an indi studio that made ArmA1/2/3 and
VBS. They work for the US government and are 2-4 times bigger than MG (140 people) but they still do not have resources/capabilities to make ArmA2 decently run with 10km visibility radius. This means to me that optimisation has its limits or becomes prohibitively expensive at some point.
For instance I remember the first time I learned about using
RAM-drive to ran a game from it. This was a solution to fix stutters in MSFS in 2000 or 2004. The problem was also the visibility distance because other games could run fine on similar hardware. In 2008/2010 the same solution was used by ArmA1/ArmA2 players to fix stutters in ArmA. Now with nextgen videocards it runs faster.