That may be true but many solutions have been introduced in plenty of Games to prevent exploits. Even funcom is working on that in Conan Exiles. Bethesda did that mistake with Physics tied to frames at first but there have been solutions that distribute the weight to the CPU instead. Modders did it. Again 
Although it requires newer CPUs that support AVX. Anyway there is alot of factors that determine a Games Engine Limits but as time goes on everything evolves.
The point is that a company can’t simply rely on the Engine itself to prevent Hacks. It needs an additional Anti-Cheat Service and there are many ways even for Encrypting Data so they can’t be Hacked by anyone. Fallout 76 was a ‘‘Rushed’’ fail. I agree with that. We’re s good old Punk Buster…