> It's completely impossible to stop cheaters these days
On that part, we can agree, and if you think I want to 'dismiss the idea' you completely misunderstood the point. My point is, that the cases anti-cheat software tries to solve, are cases that a well-designed game has solved in the beginning (e.g. sending limited game state to clients, discarding impossible input, etc.).
On the other side of the coin, I have seen players who cheated even with anti-cheat in place (like you said), for some games I was unable to play games via proton because the anti-cheat didn't work and I was unable to play some games because the developers messed up their anti-cheat implementation. So there are drawbacks to a feature that has limited use and for which many cases can be solved by other means.
In the end, there are many cheat cases that anti-cheat software can't solve (e.g. using a secondary device) and which have to be solved by other means (e.g. spectator delays, live events, private servers).