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The game booster is a smart piece of technology. It will not optimize anything, if your computer doesn't need it.
For World of Warcraft for example, because the engine was built a long time ago, even with improvements, it will trigger the Game Booster. However, FarCry 5 is a new engine and it's optimized to work on new computers, so it's not actually using that many resources, hence not triggering the Game Booster.
Check your computer CPU, GPU, memory and disk usage in WoW and FarCry and compare.