> Easy: code your game correctly and check for impossibilities server-side. But that costs money in development and infra.

Do you have any experience developing networked multiplayer games? I do it for a living, and it's not that easy, at all. In a situation where I shoot at your head on my screen, but you were already around the corner on your screen, what happens? This happens _all_ the time due to latency, and has nothing to do with development costs or infra. There's no way to avoid the problem when you have people with varying levels of connection quality, and different distances to the game server.