Ammo was never a problem in R6 games, so i'm not sure I follow that point.
Given that each character only had one gun (+ sidearm), and enough ammo that they realistically never ran out on a mission, the 'issue' of limited ammo or not is pretty irrelivent.
In games like fallout, system shock or Deus Ex, where efficent resorce managment is an important part of the game, limited ammo actually matters. Likewise, in 'traditional' FPSs like doom, where there's a specific hirachy of weapons, limited ammo for the more powerful weapons actually matters.
But for games where health and number of firearms you're able to carry at one time is limited, the effect of 'ammo' on gameplay becomes more and more moot.
You want realism? For me, the realisation that, in Vegas 2, when changing clips on an SMG lead to an extra bullet on the 'count' was due to there already being a bullet in the chamber from the previous clip made me very happy.