Based on what data do you draw that conclusion? The fact that cheaters can still exist isn't an indictment that it doesn't ever work. Have you ab tested a game with an without anti cheat?

I'm sure if you ab-tested a game with anti cheat vs a game with kernel-level anti cheat you would see negligible differences. There are a lot of types of anti cheat, stuffing it in the kernel isn't the only solution. You can't chose between security and freedom, the moment you make a choice you loose both, and other people stuffing stuff in the kernel is loosing you freedom.

We are moments away from one of these "kernel-level anti cheat" companies getting hacked and then you'll have the biggest security scandal on the planet (if they aren't already hacked and we just don't know about it yet).