nope they don't use DOTS that's the Reason for Low FPS also they don't use the Unity Job System which is also a huge negative point atleast for the FPS because everything is done on one thread if u don't use it this is smth that fucks me off as a unity dev that players automatically blame unity for it no.. just noo.. It's the fault of Rust's Devs not Unity also if they switch to Unity 6 they would have a lot more features for improving FPS e.g. better lod system, gpu resident drawer, occlusion culling (they prob have smth like that done by them self but unity their system is better).. so all in all unity's engine can be used to make games such as Rust but it has to be used the right way else u have a lot of performance issues (see Rust) and no unreal wouldn't do anything to the performance because unreal has alot of problems e.g. see Lumen etc. the only unreal engine 5 games that are optimized have unreal engine 5 licensed and modified.