I understood that you were making an analogy between installing a piece of hardware and its associated kernel driver with installing a game and its associated kernel anticheat.

When you install a hardware device you are trusting the manufacturer with full access to your machine, so installing a driver does not give them any more powers. You have already "unlocked the door".

When you install a game that runs on user space you are not trusting the vendor nearly as much as you are trusting a hardware manufacturer. Installing a kernel anti cheat is granting them a level of trust and access to your machine that they didn't have before.