The very dedicated cheaters use special PCIe hardware to alter and monitor memory through DMA, there's always a step up.
The only way to prevent cheaters is to control the hardware. With modern Xbox and PlayStation being basically a PC that you control with a controller, I can imagine a future where you buy special online gaming consoles that you control with mouse and keyboard to play competitive games. Even that can be foiled, of course, because hardware can be manipulated as well, but it's the furthest PC gaming will go.
What I wonder about it why people put so much effort into cheating. I don't see how playing more than a few games with an aimbot is any fun. What are these people even getting out of it? Is it just having their name on a board somewhere?