But for FPS games, realism is directly proportional to the hardcore level of the game

In the case of Armed Assault 3, there are a number of modules that are made to enhance the realism of the game in order to achieve a higher level of realism. Once you install these modules, you'll find that using a sniper rifle requires adjusting the closeness based on distance, and is required to calculate wind and humidity based on a ballistic solver. I'm not sure how many players will use these game designs correctly, but I'm afraid it's hard enough just to understand the terminology. The damage system in Escape from Tarkov, for example, has different effects on different parts of the body, and hand injuries on the left and right arms have different effects.