from a technical perspective gtav hacks are so easy to create and use, and so powerful (godmode, really?) because rockstar decided to make the networking model peer-to-peer so they can skimp on the server infrastructure. it has nothing to do with technical limitations (gtav game sessions are limited to 30 players anyways). in most modern games there's actually a server that receives the player actions and computes the consequences. this is why in games like counter-strike godmode isn't a thing. also valve really dedicates infrastructure to catching cheaters, even using machine learning to detect them, as opposed to feeding a bunch of teenagers to the 'dogs' for doing a lousy job of protecting their games from abuse.