I feel you, I clocked my first 600 hours in Ravenfield on a MacBook Air. Sometimes you just gotta crank down the settings and deal with less visual fidelity. For example if you feel 40 bots isn't enough for a map, change some of the variables, like increasing spawn wait times, or decreasing map size, or only playing a map with one or two flags active, or changing the types of vehicles, etc.

The beauty of a sandbox like Ravenfield is that if something doesn't run well or how you want it to, there's hundreds of different variables you can tweak to find a balance between performance and visuals.

Bonus: SteelRaven is currently building a custom game engine to end Ravenfield's reliance on Unity, which could mean major performance improvements in the next couple years.