Seeing players through walls can be solved in other ways, though. At least partially. One fix is to only draw models that the player has line-of-sight to, often with out of LOS models drawn behind the camera. Then, pop them back into place a frame before they are expected to be in LOS. That eliminates a lot of the advantages of wall hacks and model hacks. (Model hacks add a giant stick out of the front of player faces so you can see what they are looking at and, from the size/colour/whatever, how far away they are.)

Server side, you can also measure reaction time net latency to determine overly consistent or superhuman reaction times. If players aim to headshots in under 0.3s consistently, then they're hacking.

And rootkits can be beat anyway, so they're pointless, like by ruining a VM or by injecting the cheat at the bootloader, before the kernel.

And there are hardware man-in-the-middle cheats, with video capture cards sending a video stream to a companion computer running an image processing model that injects mouse commands back to the host computer.

I could keep going. There are so many ways. Trusting the client is impossible, trying to force it is unethical (requiring rootkits), and it doesn't even stop cheating! Just give up and move to server-side detection, or go back to community servers that can self moderate with human admins.

And, imho, don't even ban the cheaters—instead, flag their account to be exclusively placed into cheater-only games (with bots for filler, if needed to keep queue times roughly matched to avoid player detection). ngl, younger me (who had more time for this kind of thing) would have loved the challenge of trying to out-hack other players using cheats.