I hope you already noticed it in charts. The peak value might gain sometimes but the baseline will always be the same.
The basic reason is this - The game world is far apart from the gameplay. It doesn't follow the basic laws of the game design. You might wonder why I am saying this.
You show huge extraordinary explosions and effects, but the world around it is absolutely constant.
You want to make a 'Realistic' game (as Simulation is based on Realism rather than Fiction), yet the world has no realism in it.
There is no wind, no ambient sound, no changes in weather, no terrain displacement, no damages to building.
Everything is just phony. You had enough time to furnish the buildings with furniture or props, yet nothing happened.
Mark my word. It's not the gameplay changes, would kill your game, it's the laziness to make the actual improvement into the game world itself.
Look at other titles for instance. Do you think they have the best gunplay in the world. Yet they sell like hot cakes and have a persistent playerbase. Only because the game world feels right.
If your players need to be depended on mods to enjoy your game, I have to say you are doing it wrong.